HANDBOOK 

OF 

ELECTRICAL  METHODS 


McGraw-Hill  DookCompany 


Electrical  World         The  Engineering  andMining  Journal 
Engineering  Record  Engineering  News 

R ailway  Age  G aze tte>  American  Machinist 

Signal  EnginoGr  American  Engineer 

Electric  liailway  Journal  Coal  Age 

Metallurgical  and  Chemical  Engineering  Power 


HANDBOOK 


OF 


ELECTRICAL  METHODS 


COMPILED  FROM  THE 

ELECTRICAL  WORLD 

K 


McGRAW-HILL  BOOK  COMPANY,  INC. 
239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 
1913 


T/r  I '/ 

£5- 

Engineering 
Library 


COPYRIGHT,  1913,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY.,  INC. 


THE. MAPLE. PRESS- YOUK. PA 


PREFACE 

The  large  and  varied  amount  of  reading  matter  which  is  published  in 
a  technical  paper  like  the  Electrical  World  is  often  an  embarrassment  of 
riches  for  readers  who  do  not  make  it  a  practice  either  to  clip  and  file 
articles  which  are  of  special  value  to  them  or  to  keep  indexed  bound 
volumes.  After  all  matter  of  transient  interest  has  been  eliminated  there 
still  remain  much  data  worthy  of  more  orderly  arrangement  and  republi- 
cation  in  book  form.  The  present  compilation  is  such  a  classified  collec- 
tion of  articles  published  during  the  last  three  or  four  years  in  the  Electrical 
World  on  those  subjects  which  relate  purely  to  ways  of  doing  things 
rather  than  to  design,  descriptions  of  apparatus  or  to  the  commercial  side 
of  the  electrical  industry.  It  will  therefore  be  found  of  particular  value 
to  the  practical  man  who  is  seeking  that  kind  of  useful  information  which 
cannot  properly  be  incorporated  in  the  usual  handbooks.  The  original 
articles  have  been  edited  slightly  to  meet  the  conditions  of  publication  in 
book  form  but  no  attempt  has  been  made  to  comment  on  the  facts 
presented. 

NEW  YORK, 
December,  1913. 


2&1596 


CONTENTS 

PAGE 
PREFACE     v 

CHAPTER  I 

GENERAL  NOTES  1 

Screen  cover  for  manhole  workers — Adapting  manhole  to  new  street  grade- 
Notes  on  underground  conduit  construction — Thawing  water-pipes  with 
electricity — Thawing  water-pipes  without  a  transformer — Thawing  a 
frozen  pipe  by  electricity — Methods  of  soldering  wires  in  terminal  lugs — 
Soldered  wire  connections — Soldering  with  blow  torch  and  iron — Test-board 
proof  against  crosses  or  shorts — Protecting  gas  pipes  against  electrolysis — 
A  handy  portable  rheostat. 

CHAPTER  II 

LINE  CONSTRUCTION  AND  EQUIPMENT 15 

A  method  of  making  up  a  ground  wire — Byllesby  companies  adopt  uniform 
method  of  grounding — Ground- wire  shields  to  prevent  induction  trouble — 
Grounding  secondaries  at  Denver — Methods  of  grounding  transformer 
secondaries  and  secondary  networks — Notes  on  ground  connections — 
Pole  height  Estimator — Inspecting  inaccessible  places  with  optical  aids — 
Battery  search-lantern  for  linemen — Trouble  man's  portable  search-lamp — 
Bucket  for  bailing  poJe  holes — Blasting  holes  for  wooden  poles  with  dynamite 
— Numbering  systems  for  pins  and  cross-arms — Cross-arms  made  of  old 
pipe — Replacing  insulators  with  50,000- volt  line  "Hot" — Corner  construc- 
tion for  50,000-volt  line — Combination  brace  and  ground-wire  bayonet — 
Methods  of  splicing  wires  and  cables — High-tension  crossing  construction 
with  protective  loop — Simple  method  of  transposing  wires — Use  of  choke 
coils  with  pole  arresters — Adaptation  of  three-phase  arrester  for  two-phase 
use — Maintenance  of  electrolytic  arresters — Emergency  strain  insulators 
made  from  glass  insulators — Concrete  poles  integral  with  building  to  save 
space — Temporary  cross-arm  braces  to  aid  construction  crews — Operating 
results  with  a  2300-volt  single-wire  ground-return  transmission  line — 
Changing  35,000-volt  insulators  on  live  circuits — Concrete  resistors  for 
lightning  arresters — Raising  the  height  of  old  inclosed-arc  lamp-posts  at 
Cincinnati — Support  of  long  transmission  span  by  messenger  cable. 

CHAPTER  III 

METERS 56 

A  labor-saving  meter  truck — Tagging  meter  loops — Protection  of  electric 
meters — Two-meter  off-peak  rate — Use  of  single-phase  wattmeter  on  poly- 
phase circuit — Ohmic  and  inductive  resistances  of  meter-current  circuits — 
Pendulum  counting  device  for  testing  meters — Testing  shunt-type  watt-hour 
meters — Ammeter  testing— Testing  large  watt-hour  meters  on  fluctuating 
loads — A  portable  stand  for  graphic  instruments — Watt-hour  meter  testing 
for  central  stations. 

CHAPTER  IV 

OPERATION  OF,  AND  CHANGES  IN  CIRCUITS 77 

Operation  of  a  two-phase  distribution  system — Determining  the  power- 


viii  CONTENTS 

PAGE 

factor  of  a  three-phase  circuit — Polyphase  feeder-regulator  motors  operated 
from  single-phase  feeder  circuit — Interchangeable  connections  for  feeder 
resistance — Rearrangement  of  three-wire  system  to  reduce  voltage  fluctua- 
tions— Circuit  with  shifting  neutral  improved  by  installation  of  auto- 
transformer — Application  of  Thrill  regulator  to  adjust  balancer  for  neutral 
regulation  at  distant  point — Arrangement  of  Tirrill  regulator  to  compensate 
over  adjustable  range  of  terminal  pressures — Voltmeter  test  boxes  at  dis- 
tribution points. 

CHAPTER  V 

SWITCHBOARDS  AND  POWER  HOUSE  DETAILS 89 

Supporting  cables  in  vertical  runs — Casting  bolts  in  concrete  walls — A 
method  for  bending  busbars — A  switchboard  wiring  pit — Colored  wire  for 
switchboards  and  panels — Connection  board  for  metering  power — Connec- 
tions for.  obtaining  feeder  voltage  records — Alarm  to  indicate  operation  of 
remote  rectifier  set — Alarm  circuit  for  double-throw  oil  switches — Remote 
control  of  circuits — Stop-watch  record  of  service  interruption — Field 
excitation  test  lamps — Circular  synchronizing  bank — Relay  auxiliary  con- 
tact for  aluminum  check  cell — Balancer  set  used  to  bring  up  low  battery 
cells — Disconnect  switch  for  feeder  regulators — Extra  eye  lugs  for  dis- 
connect switches — Iron-pipe  construction  in  distribution  rack. 

CHAPTER  VI 

SIGNS,  DISPLAY  LIGHTING,  SPECIAL  LIGHTING  APPLICATIONS 105 

Remote-control  switches  for  flat-rate  signs — Interchangeable  illuminated 
sidewalk  sign — Running  boards  for  a  tungsten  lighting  installation — 
Illuminated  church  sign — Illuminated  sign  using  flaming-arc  lamps — A 
"kink"  to  save  lamps  on  series-multiple  circuits — Electric-lighted  showcase 
for  the  plate-glass  storeroom  door — Lighting  a  Chicago  store  window — 
Special  ceiling  surfaces  for  indirect  lighting — Danger  of  broken  lamp  near 
inflammable  material — An  electrical  advertising  novelty — Influencing  the 
curio  seeker's  choice  electrically. 

CHAPTER  VII 

LAMPS  AND  LIGHTING  CIRCUITS,  SIGNAL  BELL  CONNECTIONS,  ETC 116 

Lighting  one  lamp  on  four-lamp  fixtures  with  three-wire  system — Lamp 
protection — Rubber  band  prevents  lamp  from  backing  out — Lamp-cord 
adjusters — Holder  for  removing  street-series  receptacles — Cradle  clamp  for 
hanging  arc  lamps — Operation  of  series  alternating-current  street  arc 
lamps — Overcoming  overload  on  series  arc-lamp  circuits — Lamp  operation 
due  to  accidental  grounds — Locating  faults  on  series  lighting  circuits — 
Lamp  signals  for  hotel  maids — Lamp  signal  system  for  a  restaurant — Lamp 
signal  system  for  hospital— Lighting  fixtures  in  a  bank — Control  of  house 
lamps  from  central  switch — Mercury-vapor-incandescent  lamp  cabinet  for 
photographic  work — Automatic  extension  of  connection  bell — Economical 
street-lighting  wiring  arrangement — All-day  supervision  of  arc  circuits — 
Automatic  control  of  curb  lighting  fed  from  Edison  system — Remote-con- 
trolled operation  of  Peoria's  ornamental  lighting — Electric  lighting  from 
three-phase  circuits — Low-frequency  flicker  cured  by  two-phase  wiring — 
Testing  lamps  by  a  motor-driven  machine — Wiring  for  extension  lamp  in 


CONTENTS  ix 

PACK 

600-volt  series  circuit — Inexpensive  lamp  guard  for  interurban  cars — Types 
and  uses  of  semi-indirect  lighting  units. 

CHAPTER  VIII 

TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS 155 

Testing  transformers  for  insulation — Current-ratio  and  phase-angle  test  of 
series  transformers — Bridged  spark-gaps  protect  transformer  coils — Protect- 
ing secondary  networks  against  defective  transformers — Inserting  spare 
transformer  in  star-delta  group — Operation  of  tub-transformer  secondaries 
in  series — Paralleling  transformer  banks  on  star-delta  systems — The  three- 
transformer  method  of  changing  from  two  to  three  phases — Low-freezing 
mixtures  for  oil  switches — Disconnect  coupling  for  oil-switch  leads — Switch 
pull-rods  in  tension,  not  compression — Troubles  due  to  non-use  of  circuit- 
breakers — Temporary  repair  to  oil  switch — Alarm  connection  for  trans- 
formers— Two-phase  to  three-phase  auto-transformers. 

CHAPTER  IX 

INTERIOR  WIRING 174 

Removing  nails  from  trim  in  old-house  wiring — Examining  partition  interiors 
— Grounding  of  bathroom  fixtures,  etc. — Support  of  cables  for  interior  work 
— Explosion-proof  connector  plug — The  right  way  to  place  protecting  tubes 
— Right  and  wrong  methods  of  connecting  plug  cut-outs — A  method  of 
carrying  wires  around  bridges  in  old  houses — The  use  of  single-pole  switches 
— One-piece  versus  two-piece  push  switches — An  electric  iron  installation — 
Wiring  buildings  with  cinder-filled  floors.  Home-made  chandelier  hook  and 
loops — Simplifying  concealed  conduit  work— Conduit  systems  in  concrete 
buildings — Mitering  metal  molding — Erection  of  metal  molding — Wiring  in 
metal  molding — Wiring  in  cold-storage  rooms — Conduit  versus  openwork  in 
places  subject  to  moisture,  corrosive  fumes,  steam,  etc. — Insulating  and 
supporting  fixtures — Connecting  cords  in  sockets — Electric  vacuum  cleaner 
for  fishing  conduit — An  improvised  pendent  switch. 

CHAPTER  X 

MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC 229 

Motors  housed  in  external  sheet-iron — Installation  of  motors  in  dirty  places 
— Installing  motors  under  severe  dust  conditions — A  home-made  iron  switch 
box — Design  of  wooden  switch-boxes — Supporting  motors  on  concrete 
building  ceilings — Repairing  a  broken  motor  leg — Electric  welding  of  broken 
motor  shaft — Rebabbiting  motor  bearings — Care  of  electric  motors — 
Troubles  with  induction  motors — Starting  torque  of  induction  motors — 
Turning  down  a  commutator — Adjusting  interpole  fields  of  generator — Wir- 
ing equipments  for  motor  testing — Testing  polarity  of  field  coils — Testing 
magnet  coils  for  short-circuits — Commutator  testing  device — Testing  arma- 
tures with  alternating  current — Method  of  locating  grounds  in  armatures — 
Remedying  trouble  caused  by  varying  voltage — Conversion  of  550-volt  gen- 
erator to  Edison  three-wire  service — 110-volt  shunt  motor  on  a  220-volt, 
three-wire  circuit — A  method  of  raising  inverted  motors — A  safety  panel  for 
cranes — Methods  of  mounting  motors  on  side  walls  and  columns — Insulating 
and  grounding  motors  and  generators. 

INDEX  .   279 


HANDBOOK  OF 
ELECTRICAL  METHODS 


GENERAL  NOTES 

Underground  Conduit  Work,  Pipe  Thawing,  Soldering  Wire,  Electrolysis, 

Portable  Rheostat,  Etc. 

Screen  Cover  for  Manhole  Workers. — To  protect  its  workmen  in 
manholes,  where  traffic  is  dense,  the  Commonwealth  Edison  Company, 
Chicago,  provides  each  crew  with  a  screen  cover  of  the  same  size  as  the 
standard  manhole  cover.  After  the  men  have  gone  below,  this  screen  is 
dropped  into  place  on  the  sills  of  the  manhole  framing,  and  it  admits 
ventilation  to  the  underground  chamber  while  protecting  both  workmen 
and  passers-by  from  accident.  The  screening  is  of  1/4-in.  interwoven 
steel  wire  and  is  strong  enough  to  bear  the  weight  of  a  horse. 


Original  Unpaved- 
Street  Grade 


Cover 


New  Paved - 
Street  Grade 


FIG.    1. ADAPTING  MANHOLE  IN  NEW  STREET  GRADE,  MILWAUKEE. 

Adapting  Manhole  to  New  Street  Grade. — The  expense  and  trouble 
of  wrecking  the  old  concrete  cap  of  manholes  when  adapting  them  to  new 
street  grades  are  avoided  by  Richard  Krohn,  foreman  of  the  Milwaukee 
company's  underground  department,  who  employs  a  couple  of  powerful 
jacks  to  lift  off  the  concrete  cap  so  that  a  course  or  two  of  bricks  can  be 

1 


2  HANDBOOK  OF  ELECTRICAL  METHODS 

removed,  after  which"  the  cap  is  dropped  back  into  place  in  its  new  posi- 
tion. As  shown  in  Fig.  1,  the  8-ft.  by  8-ft.  by  7-in.  concrete  cap, 
weighing  2  tons,  is  handled  by  a  pair  of  2-ton  screw  jacks  blocked  up  to 
the  proper  height.  The  internal  height  of  the  manhole,  6  ft.,  leaves  ample 
room  after  subtracting  the  width  of  two  courses  of  bricks.  A  similar 
scheme  might  also  be  used  to  raise  the  cap  to  a  higher  grade.  Three  men, 
at  20  cents  per  hour,  make  the  change  in  cover  position  in  three  hours. 
To  wreck  and  rebuild  the  concrete  cover  cap  would  cost  at  least  $30  for 
labor  and  materials,  besides  requiring  several  days'  time. 

Notes  on  Underground  Conduit  Construction  (By  Guy  F.  Speer).— 
The  matter  given  herewith  is  a  collection  of  notes  taken  during  the  erec- 
tion of  an  underground-conduit  system  in  a  New  Jersey  city  with  a 
population  of  about  23,000. 

The  Conduit  Line. — The  trunk  line  extending  through  the  principal 
thoroughfare  and  business  section  of  the  town  consists  of  nine  fiber  ducts, 
laid  three  high,  with  1  in.  of  concrete  between  ducts  and  a  3-in.  envelope 
of  concrete  surrounding  them.  Extensions  of  four  ducts,  six  ducts  and 
eight  ducts  are  made  in  several  of  the  side  streets  to  manholes.  From 
these  manholes  laterals  extend  to  poles  whence  taps  are  made  to  the  over- 
head wires. 

The  longest  section  is  530  ft.  and  the  average  is  285  ft.  For  purely 
transmission  purposes  the  sections  should  run  longer,  but  for  distribution 
purposes  a  manhole  should  be  built  at  every  intersecting  street  at  least. 

At  suitable  intervals  in  the  trunk  line,  depending,  of  course,  on  the 
length  of  the  section  and  the  demands  for  service  connections  throughout 


.Curb 


Storm  Drain 


Storm  Drain 


Sec.  A-B  Dist.Hole 


FIG.    1. CROSS-OVER  BETWEEN  DISTRIBUTION  HOLES. 


a  block,  distribution  holes  or  hand  holes  should  be  installed.  On  the 
other  side  of  the  street  from  these  distribution  holes  other  distribution 
holes  should  be  built,  and  the  two  should  be  connected  by  a  four-duct 
cross-over.  (See  Fig.  1.)  In  this  manner  both  sides  of  the  street  are 
served  without  unduly  long  service  pipes  and  without  having  to  tunnel 
under  car  tracks  or  other  obstruction  whenever  a  new  service  is  cut  in. 
This  method  also  eliminates  overcrowding  of  distribution  holes.  These 
holes  should  be  spaced  on  an  average  120  ft.  apart. 

Before  beginning  excavation  on  the  line  described,  test  holes  were  dug 
from  curb  to  curb,  except  under  car  tracks,  at  street  intersections  to 


GENERAL  NOTES  3 

determine  upon  which  side  of  the  street  the  main  conduit  line  should  be 
run,  and  also  to  discover  if  space  were  available  for  constructing  manholes. 
These  test  holes  were  sunk  about  7  ft.  deep,  and  the  exact  location  of  all 
obstructions  such  as  gas  and  water  mains,  sewer  drains,  railway  and  tele- 
phone conduits,  etc.,  was  noted.  In  this  case  the  space  between  the  gas 
main  and  the  railway  conduit  was  not  sufficient  to  permit  the  building  of 
distribution  holes  and  the  main  conduit  line,  and  the  10-in.  gas  main  was 
moved  transversely  from  2  ft.  to  4  ft.  for  a  distance  of  1020  ft.  The 
task,  including  excavating,  moving  the  main,  recalking  joints,  etc., 
occupied  two  weeks  and  cost  about  $500. 

The  location  of  the  conduit  line  being  determined,  a  trench  22  in.  wide 
and  43  in.  deep  was  laid  out  to  line  and  excavated.  Theoretically  a  trench 
18.5  in.  wide  is  sufficient  for  a  nine-duct  (three-wide  and  three-high) 
line;  but  to  permit  a  man  to  work  in  the  trench  the  latter  should  be  dug 
wider.  The  lower  portion  of  the  trench  may  be  made  narrower,  however, 
and  the  depth  depends  on  the  nature  of  the  obstructions  encountered.  A 
grade  of  1  in.  in  200  ft.  is  enough  to  allow  for  drainage  into  manholes. 
Care  should  be  taken  to  avoid  traps  or  water  pockets  in  the  conduit  line. 

As  the  soil  encountered  in  building  the  line  in  question  was  hard  clay, 
no  side-bracing  or  sheeting  was  necessary.  Fiber  duct  (3.5  in.  outside 
diameter  and  0.25  in.  walls)  was  used  throughout  the  work  except  in 
crossing  through  the  roofs  of  culverts  or  large  sewers,  where  3-in.  wrought- 
iron  pipe  was  used.  Fiber  conduit  is  light  in  weight,  cheap,  easy  to  handle 
and  can  be  laid  by  unskilled  labor.  No  attempt  was  made  to  waterproof 
the  conduit,  the  concrete  envelope  forming  only  a  support  and  protection 
to  the  duct.  The  socket  joint  was  found  to  be  more  satisfactory  than  the 
sleeve  joint,  because  the  latter  required  more  time  to  fit  and  the  sleeves 
very  often  slipped  down  over  the  end  of  the  duct,  leaving  an  opening. 

After  the  trench  was  dug  a  3-in.  footing  of  concrete  was  put  in,  1 : 3 : 6 
mixture  with  3/4-in.  stone  being  used.  On  this  footing  the  duct  was  laid 
on  4.5-in.  centers,  a  "rake"  being  used  for  this  purpose.  Concrete  was 
then  rammed  between  the  ducts  and  a  1-in.  cover  of  concrete  put  on. 
This  process  was  repeated  until  the  top  layer  of  duct  was  reached,  when  a 
3-in.  cover  of  concrete  was  put  on.  The  trench  was  then  refilled,  tamped 
thoroughly  and  the  street  opening  repaved.  During  construction  care 
was  exercised  to  keep  the  conduit  as  far  as  possible  from  the  gas  main  so  as 
to  avoid  danger  of  gas  leaking  into  the  line  and  manholes  and  causing 
explosions.  Moreover,  by  this  means  danger  of  puncturing  the  ducts 
when  testing  or  " smelling"  for  a  gas  leak  is  also  eliminated. 

At  street  intersections,  in  the  middle  of  long  blocks  and  at  sharp  turns 
in  the  conduit  line  large  rectangular  concrete  manholes  were  built.  The 
sizes  constructed  were  5  ft.  by  7  ft.,  6  ft.  by  8  ft.  and  7  ft.  by  9  ft.,  with 
12-in.  walls  and  6  ft.  clear  depth.  Plenty  of  head  room  was  allowed  so  as 


4  HANDBOOK  OF  ELECTRICAL  METHODS 

to  permit  cablemen,  splicers,  etc.,  to  work  and  to  leave  space  for  the  instal- 
lation of  transformers.  Monolithic  concrete  construction  was  employed 
throughout,  a  1 : 3 : 6  mixture  with  1  1/2-in.  trap-rock  and  Portland  cement 
being  used.  The  concrete  was  put  in  quite  wet  and  rammed  thoroughly, 
especially  next  to  the  form,  so  as  to  give  a  smooth  inside  finish  when  the 
form  was  removed. 

The  frames  were  made  of  shiplap,  and  the  hard  clay  soil  eliminated 
outer  forms  and  sheeting.  Section  forms  were  not  used,  as  these  re- 
quired the  walls  to  be  built  and  the  form  to  be  taken  out  before  the  roof 
could  be  put  on.  The  walls  and  roof  were  constructed  while  the  one 
form  was  in  place,  and  after  forty-eight  hours  this  frame  was  taken  apart 
and  removed  from  the  hole.  On  5-ft.  by  7-ft.  holes  four  7-ft.  second- 
hand 4.5-in.  car  rails  were  used  to  support  the  manhole  casting  and  to 
furnish  the  bond  for  the  roof.  In  most  cases,  owing  to  lack  of  room, 
it  was  necessary  to  shelve  under  the  railway  conduit  line.  In  such 
cases  a  rail  was  placed  at  the  corner  of  the  shelf  to  take  part  of  the 
pressure  of  traffic  on  the  manhole  head.  Short  pieces  of  fiber  duct  were 
plugged  and  placed  in  walls  wherever  future  outlets  might  be  required. 

In  building  the  manholes  and  distribution  holes  enough  space  was 
left  between  the  walls  and  parallel  gas  and  water  mains  to  allow  joints  to 
be  recalked.  Circular  cast-iron  manhole  heads  with  single  cover  were  used, 
having  inside  diameter  of  36  in.  for  large  holes  and  30  in.  for  distribution 
holes.  A  film  of  cast  iron  (about  1/8  in.)  was  left  over  the  locations  of 
perforations  when  the  covers  were  cast.  In  time  the  traffic  punctures 
these  thin  coverings  and  the  cover  becomes  truly  " perforated."  The 
manhole  heads  were  set  to  the  grade  of  the  improved  street  from  data 
given  by  the  county  engineer.  Monolithic  construction  is  disadvanta- 
geous if  a  head  has  to  be  lowered  because  of  street  improvement.  In  such 
a  case  the  roof  of  the  manhole  must  be  destroyed  and  the  rails  let  down 
into  the  walls  the  required  distance. 

No  attempt  was  made  to  waterproof  the  manholes,  as  this  is  useless 
unless  the  conduit  line  is  also  waterproofed.  Sewer  connections  were  not 
provided  for  draining  the  manholes;  instead  the  water  is  pumped  out 
when  it  is  necessary  to  work  in  them.  A  cavity  is  left  in  the  floor  of  the 
manhole  to  facilitate  the  necessary  pumping  operations. 

Fig.  2  is  of  interest,  as  it  shows  five  different  styles  of  underground 
conduit — fiber,  single-tile,  multiple-tile,  "pump-log"  and  wrought-iron 
pipe. 

Distribution  Holes. — Rectangular  monolithic  concrete  distribution 
holes  3  ft.  by  4  ft.,  with  6  ft.  clear  depth,  8-in.  walls  and  6-in.  roof  and 
floor,  were  standard  throughout  the  work.  Three  ducts  of  the  main 
line  were  cut  in  for  distribution  purposes,  the  remaining  six  ducts  being 
used  for  transmission  work.  In  this  case  it  was  advisable  to  extend  the 


GENERAL  NOTES  5 

distribution  hole  down  between  the  water  main  and  the  gas  main  in 
order  to  provide  standing  room  for  workmen. 

When  no  cross-overs  are  used  it  may  be  advantageous  to  cut  in  the 
top  layer  of  duct  and  use  only  a  shallow  hand  hole  for  distribution.  It 
was  advisable  to  keep  a  side  wall  between  the  separated  duct  so  as  to 
avoid  any  possibility  of  puncturing  the  duct  when  installing  expansion 
bolts  for  angle  irons,  etc.,  later. 


Curb    _ 


30  Storm 
Drain 


FIG.    2. FIVE  DIFFERENT  STYLES  OF  UNDERGROUND  CONDUIT. 

Services. — For  services  2-in.  wrought-iron  pipes  were  used,  generally 
for  three-wire  distribution.  For  long  services  or  where  there  were 
several  bends  to  be  made  2  1/2-in.  pipes  were  employed.  Care  was  taken 
in  bending  the  pipes  to  avoid  kinks,  as  the  latter  make  drawing  in  of 

COST  DATA  ON  UNDERGROUND  CONDUIT  WORK 

Time  occupied,  months 4 

Average  number  men 40 

Trench  feet  fiber  conduit. 9,802 

Duct   feet 75,700 

Average  cost  per  duct-foot  (including  Telford  repaving,  supervis- 

sion  and  cost  of  duct) $0.16 

Service  duct  (wrought-iron  pipe),  feet 16,108 

Cost  of  services  per  foot,  average  (includes  cost  of  pipe) $0 . 25 

Distribution  holes,  3  ft.  by  4  ft.  by  6  ft 52 

Manholes,  5  ft.  by  7  ft.  by  6  ft.  and  6  ft.  by  8  ft.  by  6  ft 39 

Cost  of  distribution  hole,  average $48 . 00 

Cost  of  manhole,  average $152 . 00 

service  wires  difficult.  Generally  right-angle  "  machine  bends  "  were  used. 
A  No.  10  steel  "drawing-in"  wire  was  left  in  each  pipe  of  any  considerable 
length  or  one  having  more  than  one  bend. 

After  the  service  wires  are  drawn  in,  the  end  of  the  pipe  should 
be  cemented  or  plugged  with  oakum  and  compound  to  prevent  gas  enter- 
ing the  cellar  from  the  manhole. 

Where  a  street  is  to  be  improved  and  the  ordinance  prohibits  tearing 
up  the  street  pavement  for  a  period  of  years  it  is  advisable  to  run  pipes 
inside  the  curb  to  vacant  lots  and  buildings  where  electricity  is  not  at 
present  used.  In  cases  such  as  these  an  arrow  is  chiseled  in  the  curb  or 


6  HANDBOOK  OF  ELECTRICAL  METHODS 

sidewalk  at  the  point  where  the  service  enters,  the  direction  of  the  arrow 
indicating  from  which  hole  the  pipe  is  run.  With  the  aid  of  a  record  map 
and  these  marks  a  service  can  be  readily  "picked  up."  The  service  pipes 
were  laid  to  drain  into  manholes  or  distribution  holes. 

In  running  services  under  patent  concrete  sidewalks  it  was  convenient 
to  use  a  trench  jack  or  pipe  jack  to  force  the  pipe  from  curb  to  cellar. 
This  method  saves  time  and  leaves  the  sidewalk  unharmed.  In  rocky 
soil,  however,  its  advantages  are  doubtful,  as  a  boulder  will  turn  aside  the 
steel  nose  screwed  into  the  pipe,  and  the  pipe  will  not  strike  the  hole  cut 
for  it  in  the  cellar  wall. 

In  some  cases  because  of  obstacles  semi-reamed-out  couplings  were 
used  on  bends,  and  when  these  are  enveloped  in  cement  mortar  they  are 
satisfactory. 

Thawing  Water-pipes  with  Electricity  (By  T.  T.  Logie).— The 
accompanying  sketches  show  some  results  obtained  by  G.  H.  Caffrey, 
superintendent  of  the  Norwalk  division  of  the  United  Electric  Light 
&  Water  Company  in  thawing  pipes  with  electricity.  An  equipment 
consisting  of  a  15-kw.  transformer,  2300-volt  primary  to  110-volt  sec- 
ondary and  a  water-barrel  rheostat  was  used.  The  conductivity  of  the 
water  in  the  barrel  was  increased  by  the  addition  of  salt,  about  10  Ib.  of 
salt  to  the  barrel  being  sufficient.  Labor  expended  in  handling  was 
reduced  to  a  minimum  by  arranging  the  entire  equipment  on  a  wagon. 

a 


Curb  Box 


Service  Trap 


FIGS.    1  AND   2. THAWING  WATER  PIPES  WITH  ELECTRICITY. 

The  service  shown  in  Fig.  1  consists  of  100  ft.  of  1-in.  pipe,  laid  on  a 
grade  of  about  20  deg.  To  reach  the  street  end  of  this  pipe  it  was  neces- 
sary to  dig  down  to  the  main  at  a  point  marked  A  in  the  sketch.  At  this 
point  one  end  of  the  secondary  line  was  attached,  which  fed  through  to 
the  point  B,  where  the  secondary  circuit  was  closed.  About  150  amp.  at 
60  volts  was  allowed  to  pass  through  this  pipe  for  twenty-five  minutes 
before  water  was  obtained. 

The  conditions  met  with  in  the  service  represented  by  Fig.  2  differed 
from  those  above  in  that  the  length  of  pipe  was  double,  the  grade  very 
slight  and  the  pressure  low.  Connections  were  made  in  the  secondary 
circuit  at  the  point  A  and  on  the  valve  in  the  curb  box,  this  latter  connec- 


GENERAL  NOTES  7 

tion  being  made  by  pushing  down  a  hooked  wire  into  the  box  and 
snapping  the  hook  onto  the  wheel  of  the  valve.  From  100  amp.  to 
200  amp.  at  60  volts  was  sent  through  this  pipe  without  result  other  than 
heating  the  pipe.  The  main  was  then  uncovered  and  the  secondary 
connection  removed  from  the  curb  box  to  the  main.  This  resulted  in 
water  flowing  within  ten  minutes,  the  frozen  section  being  in  the  goose- 
neck trap  which  extended  upward  into  frozen  ground. 

A  third  station  differed  from  the  foregoing  in  that  a  fire  hydrant  could 
be  used  in  closing  the  secondary  circuit.  With  another  connection  made 
at  A  and  current  passing  through  the  pipe  for  two  hours  no  water  was 
obtained.  A  connection  was  then  made  on  the  curb-box  valve  by  the 
method  mentioned  above,  with  the  result  that  water  flowed  freely  within 
five  minutes. 


Curb-Box 


Hydrant 


FIGS.    3  AND  4. THAWING  WATER  PIPES  WITH  ELECTRICITY. 


The  house  shown  in  Fig.  4  receives  its  water  from  two  sources,  namely, 
the  street  main  in  front  of  the  house  and  through  a  barn  and  a  house  ser- 
vice on  an  adjacent  street.  The  service  from  the  house  marked  A  to  the 
barn  being  free,  it  was  a  simple  matter  to  thaw  the  remainder  of  the  ser- 
vice from  the  barn  to  the  house  marked  B,  by  making  a  connection  in  the 
barn  and  another  under  the  sink  in  the  house.  Water  flowed  in  this  sec- 
tion after  heating  the  pipe  for  four  minutes.  Another  pipe  leading  up- 
stairs was  also  frozen,  but  by  transferring  the  barn  connection  of  the 
secondary  to  the  pipe  upstairs  it  was  cleared  within  two  minutes. 

Thawing  Water-pipes  without  a  Transformer  (By  L.  N.  Jones).— 
Sometimes  a  frozen  water-pipe  is  to  be  thawed  out  in  a  place  where  no 
primary  connection  or  transformer  is  available,  or  where  it  would  be  more 
expense  and  trouble  to  set  up  the  transformer  equipment  than  the  single 
thawing  job  is  worth.  In  such  cases  the  method  used  by  E.  W.  Erick,  of 
Canby,  Minn.,  may  be  useful,  although  a  little  more  time  is  required  to  do 
the  thawing  than  by  the  usual  scheme. 


8 


HANDBOOK  OF  ELECTRICAL  METHODS 


In  freezing  several  3/4-in.  service  pipes  in  the  winter  Mr.  Erick  used 
the  contents  of  the  pipes  themselves  as  water  rheostats,  making  the 
exposed  end  of  a  No.  8  weatherproof-insulated  wire  act  as  one  of  the  elec- 
trodes. As  shown  in  Fig.  1,  several  rings  of  insulation  were  cut  from 
the  wire  to  expose  its  copper  surface,  while  a  rubber  tip  was  attached  to  its 
end,  serving  to  keep  the  metal  from  contact  with  the  pipe  which  was  con- 
nected to  the  other  side  of  the  line.  Through  the  water  path  thus 
afforded  110  volts  forced  a  current  of  from  15  amp.  to  20  amp.,  delivering 
1.5  kw.  to  2.0  kw.  near  the  front  of  the  ice  plug.  In  one  instance  16  ft. 
of  ice  in  a  3/4-in.  pipe  was  thawed  out  in  four  and  one-half  hours,  a  boy 
being  left  to  feed  in  the  wire  as  the  ice  front  retreated.  The  circuit  was 


110  Volts 


/>^^ 
FIG.    1.  -  THAWING  WATER  PIPES  WITHOUT  A  TRANSFORMER. 


protected  by  a  20-amp.  fuse,  so  that  no  damage  could  result  from  acci- 
dental short-circuit.  This  distance  of  frozen  pipe  was,  of  course,  excep- 
tional and  was  due  to  several  days'  delay  in  calling  for  assistance.  As  the 
water-rheostat  method  thaws  at  the  rate  of  3  ft.  or  4  ft.  an  hour,  only  a 
short  time  is  required  to  clear  the  usual  foot  or  so  of  frozen  plug.  This 
scheme  is  applicable,  of  course,  only  to  straight  lines,  but  as  most  service 
pipes  are  included  under  this,  the  method  will  be  found  effective  in 
most  cases.  The  natural  slope  of  the  pipe  toward  the  street  drains  the 
water  toward  the  point  where  it  forms  the  heat-producing  path,  but  if  the 
entry  is  quite  level,  a  vertical  elbow  may  be  attached  at  the  cellar  end. 
In  any  case  the  street  valve  should  be  made  ready  to  turn  off  the  supply 
when  the  ice  plug  melts  and  the  water  comes  with  a  rush. 

One  man  can  set  up  the  simple  apparatus  needed  to  thaw  pipes  by 
this  method,  and  a  boy  can  feed  in  the  wire  after  the  operation  is  started. 
The  expense  of  a  line  gang,  transformer  wagon  and  team  and  the  usual 


GENERAL  NOTES  9 

electrical  apparatus  are  all  avoided,  and  the  trouble  and  danger  of  making 
primary  connections  are  eliminated.  Mr.  Erick  has  ordered  for  future 
use  a  cartridge-type  heating  unit  of  a  diameter  small  enough  to  be  pushed 
into  the  pipe,  and  believes  that  this  will  prove  more  efficient  than  the 
simple  electrode.  To  thaw  the  16-ft.  ice  plug  above  mentioned,  8  kw.- 
hr.  to  10  kw.-hr.  was  required,  costing  about  $1  for  energy,  in  addition 
to  which  was  charged  the  time  of  one  man. 

Thawing  a  Frozen  Pipe  by  Electricity  (By  Ch.  Smeeth). — One 
winter  the  writer  was  called  on  to  thaw  out  a  2-in.  main  in  a  distant  part 
of  a  city.  It  was  ascertained  that  a  single-phase,  2300-volt  line  ran  past 
the  frozen  main,  and  that  a  30-kw.  transformer  was  available.  While 
looking  around  for  some  form  of  resistance  or  reactance  it  occurred  to  the 
writer  that  under  the  conditions  nothing  of  this  kind  was  needed  and  the 
following  method  was  successfully  carried  out: 

The  line  that  ran  past  the  frozen  main  was  disconnected  from  the 
switchboard  and  connected  to  an  idle  alternator  with  an  ammeter  in 
circuit.  The  transformer  was  then  hauled  to  the  point  where  the  pipe 
was  frozen  and  connected  up,  the  primaries  being  connected  in  the  usual 
way  and  the  secondaries  spliced  for  their  lowest  voltage,  which  was  110 
volts,  and  connected  directly  to  the  frozen  main.  The  attendant  at  the 
power  station  was  then  communicated  with  and  instructed  to  start  up 
the  alternator  slowly  (field  excited)  until  the  ammeter  indicated  15  amp. 
It  was  expected  that  under  the  conditions  the  alternator  would  be  running 
considerably  under  speed,  but  the  attendant  found  that  by  keeping  the 
exciting  current  low  he  could  run  at  usual  speed,  thus  keeping  the  fre- 
quency at  its  normal  value.  The  primary  voltage  at  the  power  house 
was  1800  volts.  Twenty-four  minutes  sufficed  to  thaw  the  pipe,  and  this 
without  reactances  or  resistances  or  trouble  of  any  kind. 

Methods  of  Soldering  Wires  in  Terminal  Lugs  (By  H.  D.  George).— 
Where  many  terminal  lugs  are  to  be  soldered  to  conductors  a  convenient 
and  time-saving  method  of  making  the  connections  is  to  melt  a  pot  of 
solder  .over  a  plumber's  furnace,  pour  the  solder  in  the  hole  in  the  lug  and 
then  plunge  the  bared  end  of  the  conductor  into  it,  as  shown  in  Fig.  1. 
The  insides  of  the  holes  of  all  commerical  lugs  are  " tinned"  so  the  solder 
adheres  to  them  readily,  and  the  bared  end  of  the  conductor  should  also 
first  be  tinned.  This  may  be  done  as  follows:  The  end  of  the  wire  is 
carefully  scraped  with  a  knife  or  a  piece  of  fine  sandpaper  (the  sandpaper 
is  best  because  it  cannot  nick  the  wire)  and  then  smeared  with  soldering 
flux  and  thrust  into  the  solder  pot.  If  a  soldering  stick  is  used  the  wire 
must  be  heated  somewhat  in  the  solder  before  the  stick  compound  will 
melt  and  adhere.  It  requires  but  a  fraction  of  a  minute  to  "tin"  the  wire 
end  in  the  pot.  After  removal  the  end  should  be  knocked  against  some 
solid  object  to  remove  surplus  solder.  Immediately  after  the  tinned  end 


10 


HANDBOOK  OF  ELECTRICAL  METHODS 


is  pushed  into  the  hole  in  the  lug  the  lug  should  be  " soused"  with  a  piece 
of  wet  waste  to  cool  it  rapidly.  The  job  is  finished  by  scraping  or  filing 
off  any  shreds  or  globules  of  solder  that  adhered  to  the  exposed  surfaces 
of  the  lug  and  by  brightening  it  with  fine  sandpaper  if  necessary. 


Bared  End 
of^Conductor 
"ready  to  be 
Thrust  in 


Section  Elevation 

FIG.    1. SOLDERING  WIRE  IN  LUG. 


The  insulation  from  the  conductor  ends  should  be  cut  back  just  far 
enough  so  that  it  will  abut  against  the  shoulder  of  the  lug,  as  suggested 
in  Fig.  2,  A.  The  appearance  is  very  unsightly  and  indicates  careless 
work  if  there  is  a  gap  between  the  shoulder  and  the  insulation,  as  at  B. 
If  because  of  some  mishap  a  connection  does  result,  having  the  appearance 


Gap 

filled  with 
Tape 


A-  Correct  B- Incorrect  C- Correction 

Method  Method  of  fault  with 

Tape 

FIG.    2. FINISHED  CONNECTIONS. 

of  Fig.  2,  B,  a  partial  correction  can  be  made  by  filling  the  gap  with  serv- 
ings of  tape,  as  shown  at  Fig.  2,  C.  The  tape  of  the  standard  7/8-in. 
width  should  be  torn  into  strips  about  1/4-in.  wide  before  applying. 
Only  enough  molten  solder  should  be  poured  into  the  hole  in  the  lug  to 
fill  it  almost  to  the  brim  when  the  conductor  is  in  position.  If  too  much 


GENERAL  NOTES 


11 


is  poured  in  it  will  be  squeezed  out  by  the  wire  and  will  flow  over  the  lug. 
It  must  then  be  removed  at  a  sacrifice  of  time. 

Another  method  of  soldering  wire  in  lugs  is  to  heat  the  lug  with  a 
blow-torch  flame,  as  outlined  in  Fig.  3.  When  the  lug  is  sufficiently 
hot  wire  solder  is  fed  into  the  hole.  The  solder  melts  and  the  bared  con- 
ductor end  is  then  thrust  into  it,  as  hereinbefore  described.  However, 
the  use  of  a  blow  torch  in  this  way  should  be  avoided  if  possible,  as  it 
blackens  the  exposed  surface  of  the  lug.  A  thorough  cleaning  with  fine 
sandpaper  is  then  necessary,  and  that  requires  more  time  than  is  justi- 
fiable. 


Wire  Solder 

being  Melted 

off  iu  Lug 


FIG.    3. MAKING  JOINT  WITH  BLOW  TORCH  AND  SOLDER  WIRE. 

Soldered  Wire  Connections  (By  F.  P.  Kenney).— The  method  of 
soldering  wires  in  terminal  lugs  as  hereinbefore  described  by  H.  D.  George 
may  prove  satisfactory  in  appearance  to  all  and  in  stability  to  some,  but 
others  will  agree  that  in  few  cases  will  it  produce  a  first-class  job.  To 
secure  proper  adhesion  between  wire,  solder  and  lug  the  temperature  of 
all  three  must  be  above  the  melting  point  of  solder  at  the  instant  of  con- 
tact. If  this  condition  does  not  exist  nothing  more  than  a  good  friction  fit 
of  all  three  parts  will  be  secured;  and  if  any  doubt  as  to  the  truth  of  this 
exists  in  the  mind  of  the  reader  let  him  apply  a  steady  torsional  strain 
to  the  wire  or  lug  so  secured. 

While  the  use  of  a  soldering  pot  as  described  is  desirable,  unless  a 
method  of  heating  both  lug  and  wire  be  employed  in  conjunction,  stability 
is  sacrificed  to  speed  and  appearance.  This  is  particularly  true  when 
the  wire  to  which  the  terminal  is  to  be  soldered  happens  to  be  a  "  stranded 
conductor,"  wherein,  to  secure  maximum  mechanical  strength  and  elec- 
trical conductivity,  it  is  absolutely  essential  that  the  solder  be  main- 
tained at  the  melting  point  until  it  has  thoroughly  permeated  the  inter- 
stices of  the  conductor. 

It  might  be  suggested  that  were  the  wire  terminal  and  lug  to  be  held 
in  the  molten  solder  until  they  had  acquired  a  temperature  equal  to  that 


12  HANDBOOK  OF  ELECTRICAL  METHODS 

of  the  solder,  the  method  described  would  be  ideal.  To  prevent  adhesion 
of  solder  to  the  outside  of  the  lug  it  should  first  be  dipped  in  a  light  oil 
of  high  flash  point,  being  careful  to  see  that  no  oil  is  permitted  to  reach 
the  inside  of  the  lug.  It  will  be  found  advisable  when  holding  the  bared 
ends  of  heavy  conductors  in  the  solder  pot  to  wrap  the  insulation  well  with 
a  rag  previously  wrung  out  in  cold  water  to  prevent  as  far  as  possible  the 
melting  of  the  insulating  compound  and  the  consequent  smearing  of  the 
terminal.  However,  any  such  drip  will  not  impair  the  joint  if  properly 
made,  though  it  will  detract  from  the  appearance  of  the  finished  job. 

Soldering  with  Blow  Torch  and  Iron  (By  C.  Jennings) . — When  soldering 
connections  between  wires  smaller  than  No.  8  many  wiremen  use  a  blow 
torch  for  heating  the  joint.  While  a  joint  can  be  made  in  this  way,  it  is 
better  to  use  a  soldering  copper  where  small  wires  are  involved.  Where 
a  blow  torch  is  used  the  insulation  on  the  conductors  is  nearly  always 
ignited  and  burns  with  a  thick  smoke  and  blackens  any  object  on  which 
it  deposits.  If  the  work  is  being  done  near  a  clean  ceiling  or  side  wall  the 
result  is  a  sooty  spot  near  the  point  where  each  joint  is  made.  It  is  prob- 
able also  that  the  excessive  heat  of  the  blow  torch  injures  the  adjacent 
insulation  of  the  conductors.  Furthermore,  the  blow  torch  is  difficult 
to  manipulate  in  restricted  locations.  A  small  alcohol  torch  is  sometimes 
used  instead  of  a  blow  torch  and  is  better  adapted  for  the  work,  but  it  is 
probably  not  as  good  as  a  soldering  iron. 

In  using  a  soldering  copper  it  is  heated  in  the  flame  of  a  blow  torch. 
To  solder  the  joint  the  hot  tool  is  placed  under  and  in  close  contact  with 
it  and  wire  solder  is  fed  into  the  turns  of  the  joint.  After  the  solder  has 
flowed  over  the  entire  surface  of  the  joint  the  iron  is  removed  and  the 
joint  is  shaken  to  throw  off  surplus  solder.  There  is  no  ignition  of  insula- 
tion and  no  sooty  smoke  where  a  joint  is  soldered  in  this  way.  The  solder- 
ing copper  can  be  used  in  confined  spaces  where  the  use  of  a  torch  would 
be  out  of  the  question.  It  is  understood  that  the  wires  to  be  soldered 
must  be  scraped  clean  and  bright  before  the  tool  is  applied.  Any  of  the 
commercial  soldering  fluxes  will  probably  be  found  convenient  as  a  flux. 

Test-board  Proof  against  Crosses  or  Shorts  (By  M.  C.  Rice).— On 
to  the  test  terminals  of  the  board  shown  110- volt  alternating  current  or 
110- volt,  250- volt  and  500-volt  direct  current  can  be  thrown  without  any 
possibility  of  short-circuits  or  crosses  between  the  several  sources  of  supply 
due  to  manipulating  improper  switches.  The  three-way,  double-pole 
knife  switch  is  mounted  on  a  pivoted  turntable  of  switchboard  marble,  like 
the  rest  of  the  panel,  and  each  jaw  closes  into  a  pair  of  contact  clips,  the 
hinge  terminals  being  connected  to  the  test  clips  as  shown.  Under  no 
conditions,  of  course,  can  the  switch  be  closed  on  to  more  than  a  single 
live  circuit.  This  Fig.  1  also  reveals  means  for  getting  one  or  both  sides 
of  the  250-500-volt  three-wire  system  by  manipulating  the  single-pole 


GENERAL  NOTES  13 

knife  switch  at  the  top.  The  turntable  switch  scheme  has  a  number  of 
similar  test-board  applications,  and  while  not  difficult  to  construct,  its 
use  will  be  found  to  save  much  wiring  complication  besides  insuring 
" foolproof"  operation. 


Test  Terminals 
FIG.    1. TEST-BOARD  PROOF  AGAINST  CROSSES  OR  SHORTS. 

Protecting  Gas  Pipes  against  Electrolysis  (By  J.  L.  Fitzhugh). — After 
a  number  of  experiments  in  the  effort  to  insulate  and  protect  its  service- 
pipe  runs  against  electrolysis  the  Laclede  Gas  Company,  of  St.  Louis, 
covers  its  wrought-iron  piping  with  layers  of  pitch  and  paper,  which  seem 
successful  in  solving  a  vexatious  problem.  The  wrought-iron  pipe,  in 
sizes  from  2  in.  to  3/4  in.,  is  first  coated  with  a  tar-and-pitch  mixture, 
heated  and  thinned  sufficiently  to  flow  easily,  and  onto  this  a  4— in. 
paper  ribbon  is  wrapped  spirally,  its  edges  overlapping.  This  paper 
covering  is  then  •  tar-painted  and  again  wrapped  with  paper,  the  proc- 
ess being  repeated  until  four  successive  coats  of  tar  and  paper 
have  been  applied.  Pieces  of  pipe  thus  insulated  have  been  placed 


FIG.    1. PROTECTING  GAS  PIPE  AGAINST  ELECTROLYSIS. 

in  the  ground  under  the  most  distinctive  conditions  of  electrolysis,  along 
with  other  lengths  not  so  treated.  After  being  taken  up  at  the  end  of  two 
years  the  unprotected  pipes  were  badly  pitted  and  almost  completely 
consumed,  while  the  insulated  piping  was  virtually  in  the  same  condition 
as  when  laid.  It  is  believed  that  pipe  so  treated  will  have  its  life  at  least 
doubled,  and  if  this  is  true  an  expenditure  for  insulation  equal  to  that  of 
the  cost  of  the  bare  pipe  is  justified.  Only  service  runs  are  being  so  treated, 
the  cast-iron  mains  being  less  subject  to  corrosion  and  electrolysis  than 
the  service  pipes.  The  tar  and  paper  coating  is  very  hard  when  cooled, 
and  the  pipe  lengths  need  be  handled  with  no  more  care  than  bare  pipe. 
The  application  to  the  pipe  is  shown  in  Fig.  1. 


14 


HANDBOOK  OF  ELECTRICAL  METHODS 


A  Handy  Portable  Rheostat  (By  A.  S.  Johnson). — A  handy  pipe- 
frame  wire-wound  rheostat  capable  of  very  finely  graduated  adjustments 
and  useful  for  many  purposes,  such  as  loading  machines,  discharging 
batteries,  etc.,  is  shown  in  the  sketch  (Fig.  1).  The  frame  is  made 
up  of  lengths  of  2-in.  iron  pipe  connected  by  the  cross-piece  and 
elbows,  and  firmly  mounted  on  a  wooden  platform,  which  may  be 
equipped  with  rollers  to  make  the  apparatus  portable.  Around  the  ver- 
tical pipes  sheet  asbestos  is  wrapped  and  on  this  is  wound  the  resistor  wire, 
in  a  single  layer,  care  being  taken  to  leave  a  slight  air  space  between  adja- 
cent turns  of  the  wire.  In  the  cross-piece,  half-way  between  the  elbows, 
a  hole  is  drilled  to  receive  the  vertical  rod  on  which  slides  the  movable 
contact,  the  lower  end  of  the  rod  being  firmly  fixed  in  the  platform.  On 
this  smoothed  rod  a  rider  is  arranged  to  slide.  This  rider  carries  a  pair 

&^z 


— 2pipe 

Wrapping 
of  Sheet 
Asbestos 


FIG.     1. A    HANDY    PORTABLE    RHEOSTAT. 

of  brass  spring  pieces  ending  in  carbon  blocks  which  bear  flatly  on  the 
turns  of  the  rheostat  wire.  The  lower  ends  of  the  resistor  coils  are  con- 
nected to  binding  posts  on  the  platform  base.  When  the  slider  is  at  the 
top  of  the  rod  all  of  the  resistor  is  in  circuit,  and  when  dropped  to  the  bot- 
tom the  resistor  is  cut  out.  The  friction  and  pressure  of  the  springs  on 
the  coils  hold  the  slider  in  position  at  any  point  desired.  As  the  carbon 
contact  blocks  bridge  several  turns  of  the  wire  there  is  no  sparking  during 
the  movement  of  the  slider  from  one  point  to  another.  The  vertical 
position  of  the  resistor  coils  assists  in  dissipating  the  heat  rapidly  by  a  sort 
of  chimney  action  and  the  margin  of  space  around  the  bottom  of  the  plat- 
form prevents  the  hot  rheostat  from  being  brought  into  contact  with 
anything  which  could  be  damaged.  Aside  from  these  points  the  rheostat 
is  inexpensive  to  build,  and  in  serviceability  will  many  times  repay  its 
cost.  The  resistor  wire  should  be  wound  in  opposite  directions  around 
each  leg  of  the  rheostat  so  as  not  to  magnetize  the  pipe  by  the  heavy 
currents  flowing. 


II 

LINE  CONSTRUCTION  AND  EQUIPMENT 

Grounding,  Methods  of  Erection  and  Identification,  Records  and  Light- 
ning Protection 

A  Method  of  Making  Up  a  Ground  Wire  (By  George  L.  Edgar).— 
Where  a  ground  wire  is  to  be  connected  to  a  pipe  and  no  ground  clamp  is 
available  the  following  method  can  be  used:  A  length,  possibly  3  ft., 
of  the  ground  conductor  is  " skinned"  and  carefully  scraped  or  cleaned 
with  fine  sandpaper.  The  pipe  on  which  the  connection  is  to  be  made  is 
filed  bright  and  clean  for  a  distance  of  several  inches  and  " tinned"  if 
the  connection  is  to  be  soldered.  Then  the  bared  end  of  the  conductor  is 
arranged,  on  the  brightened  portion  of  the  ground  pipe  as  indicated  in 


Ground 
Conductor 


\  Pipe  forming  Ground 
FIG.    1. 


Pipe  forming  Ground 

FIG.    2. 

Fig.  1.  The  free  end  of  the  wire  (c,  c,  c,  Fig.  1)  is  then  served  around  the 
pipe  as  suggested  in  Fig.  2,  and  the  free  end,  c,  of  the  wire  is  passed  through 
the  loop  B.  The  end  A  is  then  pulled.  This  draws  the  loop  B  and  the 
end  c  up  tightly  against  the  other  turns  and  effectively  prevents  the  wrap- 
ping from  unwinding.  In  an  actual  connection  the  turns  on  the  pipe  are 
wound  closely  together.  They  are  shown  separated  in  Fig.  2  better  to 
illustrate  the  method.  The  connection  can  be  soldered  with  a  blow  torch 

15 


16 


HANDBOOK  OF  ELECTRICAL  METHODS 


and  wire  solder  using  a  paste  flux  or  by  pouring  molten  solder  over  the 
connection  until  it  is  hot  enough  for  the  solder  to  adhere.  The  soldering 
pot  should  be  held  under  the  connection  during  the  pouring  to  catch  the 
solder  as  it  drops  from  the  connection.  Where  soldering  is  not  feasible 
the  connection  can  be  wrapped  with  a  couple  of  layers  of  tinfoil  and  then 
with  several  layers  of  friction  tape.  These  layers  exclude  moisture  and 
prevent  oxidation.  The  tinfoil  and  tape  should  extend  along  the  pipe  for 
several  inches  on  each  side  of  the  connection  and  should  be  wrapped  firmly 
to  form  a  moisture-proof  jacket  A  large  telephone  company  has  used 
the  tinfoil  and  tape  method  on  hundreds  of  ground  connections  for  tele- 
phone subscribers'  stations  with  excellent  results. 

Byllesby  Companies  Adopt  Uniform  Method  of  Grounding. — H.  M. 
Byllesby  &  Company's  method  of  grounding  the  secondary  circuits  of 
transformers  where  the  potential  of  such  circuits  does  not  exceed  250  volts 
is  as  follows :  All  ground  connections  must  be  made  at  the  poles  where  the 
transformers  are  installed  and  not  within  the  building  of  the  customer,  nor 
shall  the  service  switch  either  on  the  customer's  side  or  on  the  service  side 
be  connected  to  ground.  Secondary  circuits  over  1000  ft.  long  must  be 
grounded  every  1000  ft.  The  ground  connection  is  made  by  driving  a 
3/4-in.  galvanized  iron  pipe  at  least  5  ft.  into  the  ground  at  the  base  of  the 
pole,  and  more  than  5  ft.  if  permanent  moisture  is  not  obtained  at  that 
depth.  To  the  top  of  this  pipe  is  secured,  by  means  of  babbitt  metal 
poured  into  the  pipe  and  extending  therein  8  in.,  a  piece  of  No.  6  gage  BB 

G          A  i  j,fU  &  A 


Telejg^aph. 

4  4  4_ 


=  =  Ground 
FIG.    1. GROUND- WIRE  SHIELDS  TO  PREVENT  INDUCTION  TROUBLES. 

puddled  iron  wire.  This  connection  is  extended  up  the  pole,  the  wire 
being  secured  by  staples  at  intervals  of  3  ft.  For  a  distance  of  7  ft.  from 
the  ground  the  ground  wire  is  protected  by  a  piece  of  heavy  molding.  All 
single-phase,  two-wire  secondary  circuits  are  required  to  be  connected  to 
ground  on  one  side  of  the  circuit,  and  all  secondary  three-wire  circuits  are 
to  be  grounded  at  the  neutral  wire.  All  multiphase  secondary  circuits 
must  be  grounded  from  the  neutral  point  of  the  phase  connections. 

Ground-wire  Shields  to  Prevent  Induction  Trouble. — The  accom- 
panying Fig.  1  shows  the  transmission-line  construction  adopted  at  the 


LINE  CONSTRUCTION  AND  EQUIPMENT 


17 


request  of  the  owners  of  the  telegraph  and  telephone  lines,  closely  paral- 
leling which  a  right-of-way  had  been  secured  for  the  23,000-volt,  60-cycle 
circuit.  The  power-line  delta  was  accordingly  carried  on  the  far  side  of 
the  pole,  the  short-arm  extensions  on  the  telegraph  side  being  used  to 
support  a  couple  of  ground  wires,  one  above  the  other,  and  each  earthed 


L.T. 


Gr. 


L.T. 


J.F. 


L.A. 

n* 

¥ 


S.Wh.M. 


Notation 


L.T.  LightiAg  Transformer 
Wh.M.  Singlejpl 
Gr.    Ground  Wi 
L.F.   Line  ijuse 
P.F.    Primary 
J.F.    Junction 
L.A.  Lighting  A 


Fqse 


L.A 


hase  Watthour 
Wire 


Fuse 
Arre 


resters 


FIG.    1. GROUNDING  SECONDARIES  AT  DENVER. 


securely  at  every  seventh  pole.  Fear  had  originally  been  expressed  con- 
cerning induction  troubles  on  account  of  the  nearness  of  the  high-tension 
line,  but  after  several  years'  operation  no  complaint  has  yet  been  made. 

Grounding  Secondaries  at  Denver. — Among  the  larger  central-station 
systems  which  have  adopted  the  grounding  of  secondary  lighting  networks 


18  HANDBOOK  OF  ELECTRICAL  METHODS 

as  a  standard  feature  of  distribution  practice  is  the  Denver  Gas  &  Elec- 
tric Light  Company.  The  method  is  shown  in  Fig.  1. 

The  lighting  service,  which  is  of  interest  in  connection  with  the  ground- 
ing practice,  is  handled  by  multiple,  single-phase,  2200-volt  primary 
feeders  and  mains,  supplying  energy  to  secondary  networks  throughout 
the  urban  district  through  step-down  transformers  located  at  important 
centers  of  distribution  and  feeding  individual  consumers  at  110  volts  and 
220  volts,  according"  to  the  local  load  requirements. 

The  single-phase  alternating-current  system  is  made  up  of  twenty-six 
two-wire,  2200-volt  feeders  extending  from  the  station  busbars  to  the 
electrical  center  of  a  definite  section  of  the  city  which  is  electrically  inde- 
pendent of  any  other  section  or  feeder.  The  primary  mains  extend  from 
the  center  of  distribution  in  each  section  in  the  form  of  laterals  or  branches 
supplying  energy  to  the  most  remote  transformers  of  the  district  with  the 
usual  inclusion  of  intermediate  transformers  bunched,  so  far  as  practi- 
cable, to  secure  economy  of  operation  and  reasonable  first  cost.  Any 
feeder  may  be  fed  from  a  special  auxiliary  bus  in  the  station  in  case 
repairs,  adjustments  or  inspection  are  necessary  in  connection  with  the 
switches  and  regulators  in  routine  service.  Within  a  given  section  the 
secondaries  of  all  transformers  are  connected  by  three-wire  tie  lines 
forming  low-tension  busbars  from  which  the  leads  to  the  various  consum- 
ers are  tapped.  The  transformers  used  on  the  lighting  system  vary  in 
size  from  1/2  kw.  to  50  kw.,  and  all  above  1-kw.  rating  are  connected  for 
2200  volts  on  the  primary,  each  of  the  two  secondary  coils  being  brought 
out  of  the  case  and  connected  so  as  to  give  110  volts  between  the  middle  or 
neutral  line  and  either  of  the  outside  lines  and  220  volts  between  outers. 
The  company  has  found  that  with  the  load  well  balanced  considerable 
saving  in  secondary  copper  results  from  this  method  of  operation,  as 
would  obviously  be  anticipated. 

Each  transformer  is  connected  to  the  primary  main  through  outside- 
type  primary  fuses  of  double  the  transformer  rating  in  amperes.  The 
secondary  network  is  sectionalized  between  each  pair  of  transformers  by  a 
set  of  fuses  or  junction  cut-outs,  these  being  placed  approximately  at  the 
point  of  zero  current  between  the  adjacent  transformers  on  each  secondary 
interfused  section.  The  object  of  this  fusing  of  secondary  sections  is  to 
prevent  the  transformers  on  either  side  of  a  defective  unit  or  secondary 
service  from  assuming  heavy  overloads.  As  soon  as  any  abnormal  con- 
ditions arise  the  junction  fuses  on  either  side  of  a  defective  section  blow, 
as  well  as  the  primary  fuses  on  the  transformers,  and  the  section  is  auto- 
matically cleared  from  the  system.  The  junction  fuses  are  of  copper  wire, 
being  about  50  per  cent,  larger  than  the  rating  of  the  smaller  of  the  two 
transformers  between  which  they  are  in  each  instance  placed,  and  varying 
from  about  60  amp.  between  5-kw.  transformers  to  400  amp.  between  50- 


LINE  CONSTRUCTION  AND  EQUIPMENT  19 

kw.  units.  No  fuses  are  installed  in  the  neutral  lines  of  the  secondary 
networks,  although  fuses  are  placed  in  all  leads  running  from  any  wire  of 
the  secondary  service  to  consumers'  premises. 

The  company  began  grounding  in  the  residential  district  by  con- 
necting the  neutral  of  the  secondary  mains  to  the  nearest  water  hydrant 
at  intervals  of  about  two  blocks.  All  services  enter  buildings  in  Denver 
from  alleys  at  the  rear,  through  which  the  primary  and  secondary  mains 
are  carried.  The  neutral-main  ground  connection  is  made  by  a  No.  4 
B.  &  S.  copper  wire  stapled  to  the  pole  and  covered  with  weatherproof 
insulation,  the  ground  wire  being  run  down  the  pole  and  to  the  hydrant 
at  the  bottom  of  a  trench  18  in.  deep.  The  alleys  are  16  ft.  wide  and  the 
neutrals  are  usually  carried  on  35-ft.  poles  about  20  ft.  above  the  ground. 
Approximately  60  ft.  of  No.  4  wire  is  usually  required  for  the  ground 
connection  in  residence  districts,  the  maximum  length  being  125  ft.  The 
neutral  ground  wire  is  attached  to  the  hydrant  by  the  simple  process  of 
winding  it  beneath  the  footing  bolt  and  making  tight  with  a  wrench. 
In  the  down-town  section  the  usual  length  of  ground  wire  required  from  the 
secondary  network  is  from  10  ft.  to  50  ft.  The  company  has  given  up 
the  use  of  the  inclosed  fuse  in  its  secondary  mains  on  account  of  the 
cheapness  of  open  fuses.  The  total  number  of  grounds  made  on  hydrants 
by  the  fall  of  1910  was  about  150,  the  work  being  done  with  the  consent  of 
the  Denver  Union  Water  Company,  which  supplies  water  for  domestic 
and  commercial  service  within  the  city.  From  four  to  six  hydrant  grounds 
can  be  installed  per  day  by  a  force  of  two  men.  In  the  residential 
district  the  average  cost  of  making  a  ground  was  about  $4.50,  the  cost 
of  material  coming  to  $2.50 ,  with  labor  $2.  In  carrying  out  the  work  of 
grounding  it  was  found  necessary  to  put  the  current  coils  of  all  meters  in 
the  outer  leads  of  the  incoming  service,  in  order  to  protect  the  company 
against  loss  of  revenue  from  accidental  grounds  in  the  consumer's  house- 
wiring.  No  evidence  has  been  found  of  the  disintegration  of  the  hydrant 
grounds  and  no  perceptible  expense  of  maintenance  has  been  found  to 
exist  in  connection  with  the  grounding  system. 

By  regulation  of  the  municipal  authorities  early  in  1911  all  new 
electric-lighting  installations  are  required  to  ground  their  neutral  wires, 
the  owner  and  wiring  contractor  being  responsible  for  this  work.  All 
wiring  in  new  buildings  is  required  to  be  in  iron-armored  conduit,  and 
where  possible  concealed  wiring  in  old  buildings  is  required  to  be  installed 
in  this  manner.  The  city  requires  conduit  to  be  permanently  and 
effectively  grounded  in  such  a  manner  that  in  case  either  wire  comes  in 
contact  with  the  conduit  and  a  ground  exists  on  the  opposite  polarity  it 
will  be  able  to  operate  the  heaviest  fuse  before  burning  off  the  ground. 
This  ground  is  usually  made  by  bonding  the  conduit  to  the  water  pipe. 
Grounding  to  steam  or  gas  pipes  is  not  allowed.  An  insulating  joint  and 


20 


HANDBOOK  OF  ELECTRICAL  METHODS 


canopy  ring  are  required  to  insulate  the  fixture  proper  from  the  conduit. 
When  fixtures  or  sockets  are  installed  over  cement  or  grounded  floors,  or 
in  places  where  they  can  be  reached  from  grounded  parts  of  bathrooms, 
stoves,  ranges,  etc.,  porcelain  sockets  are  required  to  insure  safety  while 
turning  on  the  lights.  The  ground  wire  connecting  the  conduit  with  the 
water  pipe  cannot  be  smaller  in  circular  mils  than  one-half  the  main  feed 
wire.  A  special  clamp  is  provided  for  grounding  the  neutral  wire  to  the 
cabinet  box  and  conduit  system  in  the  box,  just  inside  the  building  in  each 
case.  The  company's  experience  indicates  that  the  grounding  of  lighting 
secondaries  up  to  a  point  where  the  maximum  potential  between  any 
lead  and  ground  does  not  exceed  150  volts  is  an  excellent  precautionary 
measure. 


Arm  Carryingr- 

Primary  Circuit. 

Transformer.- 


t.         y  —  t 

1,             Soldered 

-  —  ^r^^ 

W 

-^"Connection  . 

MA 

£= 

1 

L 

Arm  Carrying 
Three-Wire 
Secondary  Circuit. 

~"           -Galv.  Iron 

j 

ipe  Straps. 


Galv.  Steel  Stranded 
Guy  Cable. 


%  Galv.  Iron  Pipe. 


End  Pointed. 


FIG.    1. METHOD    OF    GROUNDING 

SECONDARY. 


_  7/ie  Std. 
"*     Messenger 
Cable. 

JFill  with 
•^   Solder. 


Plug  with 
"Soft  Wood. 


JT  Galv. 
Iron  Pipe. 


FIG.    2. METHOD  OF  CONNECT- 
ING CABLE  TO  PIPE. 


Methods  of  Grounding  Transformer  Secondaries  and  Secondary 
Networks  (By  Harold  P.  Jennings). — Ground  connections  can  be  made 
in  many  ways.  They  may  be  made  inside  of  buildings  by  connecting  to 
pipes  or  may  be  installed  at  the  poles  which  support  the  transformers  or 
the  secondary  networks.  Central-station  practice  favors  grounds  at 
poles.  Figs.  1  and  2  show  the  method  of  making  a  pole  ground  for  aerial 


LINE  CONSTRUCTION  AND  EQUIPMENT 


21 


secondaries  used  by  the  Allegheny  County  Light  Company,  of  Pennsyl- 
vania. The  lower  end  of  the  pipe  is  pointed,  the  upper  end  is  " tinned" 
inside,  and  the  wooden  plug  is  inserted  in  the  company's  shop.  In  mak- 
ing a  ground  the  pipe  is  driven  into  the  earth  next  to  the  pole  and  the  steel- 
cable  ground  conductor,  its  end  having  been  tinned,  is  soldered  into 


Transformer  Secondary  Windings 
Two-Wire  Three- Wire 

Single-Phase 


Delta 


Star 
Three-Phase 


Open-Delta 


Four-Wire  Three-Wire 

Two-Phase 

FIG.    3. THEORETICAL  DIAGRAM  OF  SECONDARY  GROUND  CONNECTIONS. 

the  upper  end  of  the  pipe  by  pouring  molten  solder  in  around  it.  An  ex- 
cellent feature  of  this  method  is  that  the  7/16-in.  ground  conductor  is  so 
strong  that  it  will  never  be  disturbed.  It  is  secured  to  the  pole  with  pipe 
straps. 

The  ground-pipe  cap  illustrated  in  Fig.  4  is  used  by  several  large 


No.6 
Ground  Wire 


Galv. 
Malleable 
Iron  Cap 


W  Galv. 
Iron  Pipe 


Ground  Wire         Ready  for  Elevation  Section 

and  Cap  Driving  Completed  Joint 

FIG.    4. MAKING  CONNECTION  WITH  GROUND-PIPE  CAP. 


central-station  companies  for  connecting  the  ground  wire  to  the  ground 
pipe.  Soldering  is  not  necessary.  The  cap  with  the  wire  in  position  is 
placed  over  the  top  of  the  pipe  and  the  pipe  is  driven.  In  driving  the 
wire  is  firmly  wedged  between  the  cap  and  the  pipe.  The  cap  fits  a  1/2- 
in.  pipe  or  3/4-in.  rod,  with  a  No.  6  ground  wire.  Where  No.  4  wire  is 


22 


HANDBOOK  OF  ELECTRICAL  METHODS 


used  it  is  not  necessary  to  double  it.  Ground  pipes  must  be  long  enough 
to  reach  permanently  moist  soil,  and  in  driving  care  must  be  taken  not  to 
drive  them  into  the  pole  and  thereby  insulate  them.  Some  companies 
ground  to  fire  hydrants.  The  ground  wire  is  supported  down  the  pole  by 


/\t      fWA/^A/v^/     | 


"  G  round  Connection 
Single-Phase  110  Volts 


-& 


220  Volts  * 


~  Ground  Connection 
Three-Wire  110-220  Volts 


Secondary  Windings 

\~f~-~r^ 


Connection 
Single-Phase  220  Volts 


Three-Phase  Delta  Connection 


Three-Phase  Star  or  Y  Connected 

FIG.    5. GROUND  CONNECTIONS  TO  SECONDARIES  OF  COMMERCIAL 

TRANSFORMERS. 

cleats  or  straps  and  is  carried  in  a  trench,  possibly  18  in.  deep,  to  the  fire 
hydrant.  It  is  connected  thereto  by  clamping  it  under  a  footing  bolt. 
In  Denver  this  method  costs  $4.50  per  ground,  the  average  length  of 
ground  wire  required  from  pole  top  to  ground  being  60  ft. 

Ground  wires  should  be  incased  by  wooden  molding  for  a  distance  of 
at  least  7  ft.  from  the  surface,  to  protect  against  shocks  to  passers-by. 


LINE  CONSTRUCTION  AND  EQUIPMENT  23 

Under  certain  conditions  of  soil  moisture  a  shock  can  be  received  from  a 
ground  wire  by  a  person  standing  on  the  earth's  surface.  The  ground  pipe 
extends  about  a  foot  above  ground  and  is  not  usually  protected.  Some 
companies  incase  the  entire  length  of  the  ground  wire  in  molding  to  pro- 
tect the  linemen. 

No  wire  smaller  than  No.  6  should  be  used  for  a  ground  wire,  and  some 
companies  use  nothing  smaller  than  No.  4.  Copper  wire  is  preferable. 
Bare  wire  is  satisfactory  and  should  be  attached  to  the  poles  with  cleats 
or  straps.  Staples  should  not  be  used.  The  National  Electrical  Code 
requires  for  three-phase  systems  that  the  ground  wire  be  of  the  same  carry- 
ing capacity  as  any  one  of  the  three  mains.  There  should  be  a  ground  for 
each  transformer  or  group  of  transformers,  and  when  transformers  feed 
a  network  with  a  neutral  wire  there  should  in  addition  be  a  ground  at  least 
every  500  ft. 

Ground-wire  connections  to  transformer  secondaries  should  be  made 
to  the  neutral  point  or  wire  if  one  is  accessible.  Where  no  neutral  point 
is  accessible  one  side  of  the  secondary  circuit  may  be  grounded,  provided 
the  maximum  difference  of  potential  between  the  grounded  point  and 
any  other  point  in  the  circuit  does  not  exceed  250  volts.  Fig.  3  shows 
theoretical  diagrams  of  ground  connections  to  transformer  secondaries, 
and  Fig.  5  illustrates  how  some  of  these  connections  are  arranged  with 
commercial  transformers.  The  neutral  point  of  each  transformer  feeding 
a  two-phase,  four-wire  secondary  should  be  grounded,  unless  the  motors 
taking  energy  from  the  secondary  have  interconnected  windings.  Where 
they  are  interconnected  the  center  or  neutral  point  of  only  one  transformer 
is  grounded.  No  primary  windings  are  shown  in  Figs.  3  and  5.  In  Fig. 
5  the  secondary  winding  of  each  transformer  is  shown  divided  into  two 
sections,  as  it  is  in  commercial  transformers. 

Some  Notes  on  Ground  Connections  (By  E.  H.  Holmes). — It  is 
quite  well  established  that  it  is  of  the  greatest  importance  that  ground  con- 
nections be  well  made.  It  has  been  the  experience  of  men  that  have 
investigated  lightning-arrester  troubles  that  many  are  caused  by  imperfect 
earth  connections.  The  best  arrester  equipment  purchasable  may  be 
installed,  but  if  the  earth  connection  is  not  good  the  arrester  cannot  be 
expected  to  do  its  work  properly.  The  cost  of  the  earth  connection  is 
usually  but  a  fraction  of  that  of  the  arrester.  Money  spent  in  arranging 
a  good  earth  connection  is  very  well  spent  and  it  is  just  as  important  that 
a  lightning  arrester  have  a  good  ground  as  it  is  that  the  arrester  itself  be 
good. 

In  Fig.  1  is  illustrated  a  good  method  of  constructing  a  ground  rod. 
It  is  one  that  has  been  used  by  telephone  and  electric-lighting  companies 
to  a  considerable  extent.  The  rod  is  of  commercial  rolled  iron,  and  a 
diameter  of  1/2  in.  or  5/8  in.  is  usually  chosen.  Wrought-iron  pipe, 


24 


HANDBOOK  OF  ELECTRICAL  METHODS 


either  plain  or  galvanized,  can  be  used  instead  of  iron  rod.  A  length  of 
copper  wire  is  soldered  to  the  upper  end  of  the  rod,  as  indicated  in  Fig.  1, 
and  the  lower  end  is  pointed.  Such  a  rod  should  be  from  5  ft.  to  7  ft.  long. 
It  will  be  found  most  economical  to  solder  the  lengths  of  wire  to  the  rods  at 
the  station,  where  the  proper  appliances  usually  are  available.  At  best, 
it  is  not  easy  to  solder  to  iron,  so  that  for  satisfactory  results  the  operation 
should  be  performed  under  favorable  conditions. 

In  soldering,  the  upper  end  of  the  rod  should  first  be  filed  until  it  is 
quite  clean  and  bright.  All  traces  of  scale  and  oil  must  be  removed. 
Then  it  must  be  heated  in  the  flame  of  a  blow-torch  until  solder  will 
melt  when  applied  to  it.  The  hot  end  should  now  be  rubbed  in  a  pile  of 


Tile  one  face  smooth 

for  Lug  1 

a 


Wire  Soldered 


Tin  end  of  Rod  thoroughly 
before  trying  to  Solder  on  Wire 


\ 


Method  of  Winding  on  Wire 


This  should 
be  tinned-i 

and  sweated 
on  to  pipe 


Ground 


Round  Iron  Rod 


Form  Point 
on  End 


Eye  End  ffl 


Complete  Ground  Rod 
FIG.    1. WROUGHT-IRON  GROUND  ROD. 


FIG.  2. COMMERCIAL   "EYE-END  "   ON  PIPE. 


powdered  sal-ammoniac,  which  will  clean  it  chemically,  and  solder  wire 
should  be  applied  simultaneously.  The  end  will  "  take  "  the  solder  readily 
and  soon  become  " tinned."  The  end  of  the  length  of  copper  wire  can 
now,  after  being  well  cleaned  with  sandpaper,  be  wound  around  the  tinned 
portion  in  the  manner  indicated  in  Fig.  1  and  bolder  again  applied.  Solder 
will  flow  over  the  wire  and  effect  a  good  electrical  connection  between  it 
and  the  pipe  or  rod.  The  completed  joint  can  be  cooled  quickly  with  a 
piece  of  wet  waste. 

Ground  rods  are  installed  by  merely  driving  them  into  the  earth. 
The  ground  wire  from  the  lightning  arrester  or  other  device  to  be  grounded 
is  connected  and  well  soldered  to  the  length  of  copper  attached  to  the 
ground  rod.  There  is  never  much  difficulty  in  soldering  two  pieces  of 
copper  wire  together.  When  a  ground  rod  is  being  driven  the  blows  from 
the  driving  hammer  tend  to  make  it  vibrate  transversely.  The  effect  of 
such  vibrations  is  to  push  the  earth  away  from  the  rod  and  to  make  the 
connection  between  them  poor.  Therefore,  after  driving  it,  the  earth 
around  a  ground  rod  should  be  well  tamped. 

In  the  following  table  are  shown  some  ground-rod  resistance  values — 
the  resistance  in  ohms  between  driven  ground  rods  and  a  town  water-pipe 
system — which  indicate  the  effect  of  thorough  tamping. 


LINE  CONSTRUCTION  AND  EQUIPMENT 


25 


Resistance  before 
tamping 

1600  ohms 
1800  ohms 
1550  ohms 
1950  ohms 


Resistance  after 
tamping 

59  ohms 
83  ohms 
72  ohms 
90  ohms 


These  results  are  from  some  tests  made  on  Long  Island,  New  York. 
The  formation  was  about  2  ft.  of  dark  soil  above  a  thick  layer  of  sandy 
gravel.  These  resistance  values,  even  after  the  ground  had  been  tamped, 
are  rather  high.  A  good  rod  or  pipe  ground  should,  under  favorable 
conditions,  have  not  more  than  15  ohms  to  30  ohms  resistance. 

In  Fig.  2  is  illustrated  a  method  of  providing  a  pipe-ground  rod  with  a 
terminal.  The  terminal  is  a  commercial  awning  pipe  fitting  known  as  an 
"  eye-end."  This  fitting  is  made  in  all  standard  pipe  sizes  from  1/4  in. 
to  1  in.,  inclusive,  and  is  tapped  with  a  standard  pipe  thread.  This 
arrangement  is  convenient  where  it  is  desirable  to  disconnect  the  ground 
lead  from  the  pipe  so  that  the  ground  can  be  tested.  A  terminal  lug 
should  be  soldered  to  the  end  of  the  ground  lead.  The  lug  is  tightly  bolted 
to  the  "  eye-end."  Then  tinfoil  is  wrapped  about  the  connection  to 
exclude  moisture  and  the  whole  thoroughly  taped.  A  bolted  connection, 
made  as  suggested,  will  remain  in  excellent  condition  for  a  surprisingly 
long  time.  It  should,  however,  be  inspected  when  the  ground  is  tested. 
It  is  necessary  to  disconnect  the  lead  from  a  ground  pipe  to  test  the  ground 
resistance  when  the  pipe  forms  one  of  a  group,  such  as  is  used  in  a  multiple- 
pipe  ground.  A  diagram  of  a  multiple-pipe  ground  is  shown  in  Fig.  15. 


O 


Wall  Plate  Flat  Wall  Plate  Eye  Stub  Nut  End 

FIG.    3. FORMS  OF  COMMERCIAL  AWNING  FITTINGS. 


Round  Socket 


Other  forms  of  awning  fittings  that  sometimes  can  be  utilized  in 
arranging  pipe  grounds  are  shown  in  Fig.  3.  All  of  these  can  be  obtained 
in  either  black  or  galvanized  finish,  and  all  have  standard  pipe  threads. 
The  commercial  name  by  which  each  fitting  is  known  is  given  under  it  in 
the  engraving. 

In  Fig.  4  is  indicated  the  method  of  preparing  a  station  ground 
forlightning  arresters  as  recommended  by  one  of  the  large  electrical  manu- 
facturing companies.  The  ground  plate  is  of  sheet  copper,  tinned,  and 


26 


HANDBOOK  OF  ELECTRICAL  METHODS 


should  be  about  1/32  in.  thick.  The  ground  wire,  which  should  be  equal 
in  conductivity  at  least  to  No.  0  B.  &  S.  gage  wire,  is  soldered  on  the  entire 
width  of  the  plate.  An  old  iron  casting  having  a  superficial  area  at  least 
equal  to  that  of  the  copper  plate  can  be  used  if  copper  is  not  available. 
For  a  terminal  a  copper  strap  can  be  riveted  to  the  plate.  It  is  recom- 
mended that  when  the  hole  is  being  filled  in  plenty  of  water  be  used  for 
settling  the  earth. 

A  great  many  grounds  are  made  by  the  telephone  companies  for  the 
telephone-station  lightning  arresters.     Where  possible  a  connection  is 


— 4- 


Outline 

of 
xcavation 


£-  -     3'2"±  - 

—^ 

fj 

—  1 

1  |    Ground  Wire 

V 

Ml 

1    | 

ii_ 

y 

l- 


Ground  Plate 


Plan 

Surface  of  Earth- 


Hole  must  be 
deep 

that  Plate 
always  be    Sx 
Moist 


Section 

FIG.    4. COPPER-PLATE  GROUND. 

made  to  a  water  or  gas  pipe  with  one  of  the  many  types  of  commercial 
ground  clamps.  In  rural  districts  either  ground  rods  or  ground  plates  are 
used.  Some  companies  use  ground  rods  such  as  that  shown  in  Fig.  1. 
Other  companies  prefer  plates.  Fig.  5  shows  the  ground  plate  used  by  one 
of  the  largest  Eastern  telephone  companies.  It  is  very  much  cheaper  to 
install  rods  than  plates  because  a  rod  can  be  driven  into  the  ground  in  a 
few  minutes,  while  it  may  take  one  hour  or  several  to  dig  the  hole  for  a 
ground  plate.  Plates  like  that  of  Fig.  5  are  for  telephone  work,  buried 
from  4  ft.  to  6  ft.  deep  directly  in  the  soil  without  any  coke  packing  at  the 
bottom  of  a  hole. 


LINE  CONSTRUCTION  AND  EQUIPMENT 


27 


Telephone  central-office  grounds  must  be  good  ones.  As  a  rule,  a 
connection  is  made  to  both  gas  and  water  pipes  when  the  two  are  avail- 
able. Fig.  6  shows  the  method  of  effecting  a  connection  with  a  water 


Slots  CaTt 
in  Plate  arid 
Wire  Wove|n 

through  r 


Soldered  to  Ground  j 
I  Plate  and  Painted    | 
|     with  Asphultum 
I 


Copper 
Plate 


No.  16  B.&  S.Wire  for  one 
Arrester  o-r  No  10  or  6 
for  a  Group  of  Arresters 

FIG.  5.  -  A  COPPER  GROUND  PLATE. 


pipe  that  has  been  used  by  some  of  the  largest  telephone  companies. 
A  special  brass  plug  (see  Fig.  7  for  details)  is  turned  into  a  tee  in  the  pipe 
system  and  a  terminal  lug  on  the  end  of  the  ground  lead  is  sweated  and 
bolted  to  it.  Such  a  connection  is  always  made  on  the  street  side  of  the 


FIG.    6. GROUND  ON  A  WATER  PIPE. 


FIG.    7. BRASS  GROUND  PLUG. 


shut-off  cock  and  of  the  meter  so  that  the  removal  of  either  of  these  mem- 
bers cannot  effect  the  continuity  of  the  ground  connection.  Sometimes 
a  connection  to  a  water-pipe  is  made  by  soldering  a  copper  strap  around 
the  pipe  and  then  connecting  the  ground  lead  to  the  strap.  It  is  extremely 


28 


HANDBOOK  OF  ELECTRICAL  METHODS 


difficult  and  not  always  altogether  safe  to  solder  to  a  pipe  that  is  full  of 
water. 

Another  form  of  ground  that  has  been  used  by  some  of  the  big  tele- 
phone companies  is  detailed  in  Figs.  8  and  9.     A  ground  of  this  type  is 


&--.  Ground  Plate 
U —          — 3'Square  —          — »| 

FIG.    8. — GROUND  MADE  WITH  A  COPPER  SPIRAL. 


ands  No.10 
B.&  8. Gauge 
Copper  Wire  or 
Equivalent. 

f" 


Copper  Wire  j 

is  Soldered     | 

across  of  Platel 


Soldered  Connection  between*  °°WP» 

Copper  Wire  and  Plate  is  JJ  IMong, 

thoroughly  Painted  with  -020  thick. 

Asphaltum. 

FIG.    9. DETAILS  OF  A  COPPER  SPIRAL. 


sometimes  arranged  under  the  basement  floor  of  a  central  office,  as  shown 
in  Fig.  8.  This  procedure  appears  to  be  satisfactory  where  there  is  every 
assurance  that  the  earth  surrounding  the  copper-ground  spiral  will  always 
be  moist.  The  writer  has  been  given  to  understand  that,  even  when  this 


LINE  CONSTRUCTION  AND  EQUIPMENT 


29 


type  of  ground  is  installed  out  of  doors,  a  layer  of  concrete  1  ft.  in  thickness 
is  placed  at  the  surface  over  the  spiral  to  maintain  the  ground  lead  in 
position  and  to  prevent  any  tampering  with  the  lead  or  with  the  copper 
spiral,  which  is  shown  in  Fig.  9. 

Common  salt  mixed  with  the  earth  surrounding  a  ground  pipe  or 
plate  decreases  the  resistance  of  the  ground  much  below  that  of  a  similar 


1234567 
Time  (Elapsed)  in  Days 

FIG.    10. CURVE  SHOWING  EFFECT  OF  " SALTING. 


Section  of 

Sewer  Pipe         Cover 


FIG.    11. A  'SALTED'     PIPE  GROUND  UNIT. 


but  unsalted  one.  The  curve  reproduced  in  Fig.  10  brings  out  this  fact. 
The  ground  from  which  the  values  plotted  were  obtained  was  made  by 
driving  a  pipe  5  ft.  into  the  earth.  At  the  surface  the  soil  was  scooped 
out  around  the  pipe.  In  this  cup-shaped  depression  4  Ib.  of  salt  was 
dumped.  Salt  and  water  were  subsequently  added  as  indicated  on  the 


30 


HANDBOOK  OF  ELECTRICAL  METHODS 


curve.  It  will  be  noted  that  the  original  resistance  of  the  unsalted  ground 
was  about  48  ohms,  but  that  it  was  reduced  by  the  addition  of  salt  and 
water  to  something  less  than  15  ohms.  As  the  salt  is  washed  out  of  the 
surrounding  soil  by  rain  the  resistance  of  the  ground  will  gradually 
increase. 

To  take  advantage  of  the  property  of  salt  in  decreasing  ground  resist- 
ance a  form  of  pipe-ground  unit  similar  to  that  shown  in  Fig.  11  has  been 
suggested.  A  ground  pipe  having  a  nominal  diameter  of  about  1  in.  is 
driven  into  the  earth  a  distance  of  about  6  ft.  and  a  length  of  sewer  pipe 
arranged  around  its  top,  as  shown  in  Fig.  11.  A  wooden  cover  fits  in  the 
shoulder  on  the  sewer  pipe.  The  ground  lead  is  connected  to  the  pipe 


Lock  Nuts 
and  end  of 

Pipe  should 

be  Tinned 

before 

Assembling 


Terminal 
Lug 

FIG.    12. ONE  METHOD  OF^CONNECTING 

TO  GROUND  PIPE. 


Plate  / 
Soldered 
to  Lock- 
Nuts 


Terminal 

Lug 
Steel  Bolt 


Ground  Pipe 


FIG.  13. ANOTHER  METHOD  OF  CON- 
NECTION. 


by  means  of  the  arrangement  illustrated  in  Fig.  12.  This  permits  the 
lead  to  be  readily  disconnected  so  that  the  ground  may  be  tested. 
A  supply  of  salt,  which  will  soak  into  and  saturate  the  surrounding  earth, 
is  maintained  in  the  sewer-pipe  chamber.  Where  the  ground  lead  is  not 
of  heavy  wire  and  can  be  easily  bent,  a  simple  connecting  arrangement, 
outlined  in  Fig.  13,  can  be  used.  It  can  also  be  used  where  the  ground 
lead  leaves  the  pipe  in  a  horizontal  direction  instead  of  in  a  vertical  one, 
as  in  Fig.  11. 

It  was  suggested  above  that  the  ground  pipe  should  be  driven  to  a 
depth  of  about  6  ft.  Experiments  show  that  little  is  to  be  gained  by 
exceeding  this  depth.  The  resistance  of  a  pipe  ground  does  not  vary 
inversely  as  the  depth  in  a  simple  ratio.  For  the  first  few  feet  driven  the 
resistance  decreases  rapidly  for  each  additional  foot  of  depth,  but  as  the 
depth  increases  the  resistance  decrease  is  less  rapid.  The  resistance  is 
almost  constant  for  depths  greater  than  7  ft.  or  8  ft. 


LINE  CONSTRUCTION  AND  EQUIPMENT 


31 


The  practice  of  making  multiple-pipe  grounds  is  largely  followed.  A 
multiple-pipe  ground  (Fig.  15)  consists  of  a  number  of  pipe-ground  units, 
similar  possibly  to  that  of  Fig.  11,  connected  in  parallel.  The  resistance 
of  such  a  group  is  much  less  than  that  of  any  single  unit  in  it.  In  arrang- 
ing ground  units  one  should  be  located  as  near  as  possible  to  the  lightning 


Penstock 


Ground  Units 
(See  Eig.U) 


Wall  of  Station 


To  Frames  of 
Generators 


^  Connection  to 
|    Steel  Frame 
\     in.^Building    /  

To  Lightning      \ 
Arresters 

t        -                               r* 

/                     ^4          , 

}      („>„„„„„„,„*/; 

fa.         ,^j 

~     i 

Buried 

Ground 

Wire 


-O 


Connection  to 
Water  Pipes 
in  Building 


O  CO 

FIG.    14. GROUND  UNITS  AROUND  A  GENERATING  STATION. 

arrester  and  the  others  grouped,  as  in  Fig.  14,  around  the  building. 
Auxiliary  ground  leads  should  be  connected  to  the  metal  frame  of  the 
building,  to  any  available  water  and  gas  pipes  and  to  the  penstock  or 
pipe  line  if  the  plant  is  operated  by  water-power.  Ground  connections 
are  also  made  to  the  frames  and  cases  of  apparatus  to  be  protected. 


,  Surface 


Ground  Pipe        .Ground  Wire 


Wire  Soldered 
to  Pipe 


To  next 

Ground 

Pipe 


FIG.    15. ONE  METHOD  OF  MAKING  MULTIPLE-PIPE  GROUND  CONNECTION. 

A  method  of  connecting  multiple-pipe  grounds  together  less  elaborate 
than  that  illustrated  in  Figs.  12  and  13  is  shown  in  Fig.  15.  In  this 
simple  method  the  ends  of  the  ground  pipes  are  tinned,  as  described  in 
connection  with  Fig.  1,  before  they  are  driven.  After  driving,  the  bare 


32  HANDBOOK  OF  ELECTRICAL  METHODS 

copper  ground  wire  that  is  to  connect  the  pipe  ends  together  is  wrapped 
around  each  pipe  in  succession  and  soldered  thereto.    . 

Pole-height  Estimator. — To  insure  accuracy  in  pole  lengths  the  line 
department  of  The  Milwaukee  Electric  Railway  &  Light  Company  is 
making  use  of  a  pole-height  estimator,  a  pocket  device  originated  b}^ 
S.  B.  Way  and  J.  L.  Fay,  of  the  company,  with  which  an  ordinary  lineman 
can  sight  over  the  object  to  be  crossed  and  read  directly  on  a  scale  the 
pole  required  to  give  5-ft.  clearance  when  set  in  the  ground  to  the  proper 
depth.  The  estimator  is  similar  in  optical  principle  to  the  mariner's 
device  for  reading  star  ascensions,  although  simplified  and  arranged 
with  scale  calibrated  directly  in  pole  heights.  To  use  the  estimator,  the 
lineman  measures  with  tape  or  by  pacing  a  distance  of  50  ft.  from  the 


FIG.    1. POLE  HEIGHT  ESTIMATOR. 


point  beneath  the  tree  or  obstacle,  and  then,  from  this  distance,  sights 
through  the  estimator  tube  at  the  tree-top  or  obstructing  line.  The 
turning  of  a  knurled  thumb-screw  at  the  side  rotates  a  level  until  its 
bubble,  seen  in  a  45-deg.  mirror,  appears  alongside  the  center  of  the  tube. 
After  bubble  and  object  have  been  sighted  together  in  the  tube,  the 
pointer  shows  on  the  calibrated  scale  the  exact  height  of  the  pole,  in- 
cluding clearance  and  setting  allowances.  Twenty-five-foot  poles  are 
provided  to  be  set  4.5  ft.  in  the  ground,  45-ft.  poles  6  ft.,  and  75-ft.  poles 
7.5  ft.,  with  proportionate  amounts  for  intermediate  heights.  The  esti- 
mators weigh  only  a  few  ounces  and  can  be  carried  in  the  vest  pocket. 
A  drawing  of  an  estimator  is  shown  in  Fig.  1 . 

Inspecting  Inaccessible  Places  with  Optical  Aids  (By  J.  L.  Johnson). 
—To  inspect  insulators  and  line  construction  a  pocket  glass  will  save 
much  climbing  of  poles  or  towers.  A  conductor  down  on  the  ground  can 
be  seen  miles  away  across  open  country.  An  aid  to  estimating  distances 
in  this  case  is  a  pair  of  spiders'  webs  stretched  across  the  field  of  view  in 
the  focal  plane,  the  interval  between  the  cross-hairs  being  made  such  as  to 
subtend  a  man's  height,  say  6  ft.,  at  a  known  distance — half  a  mile  or  a 
mile.  A  man,  a  house,  a  window  or  a  door  can  be  picked  up  in  almost  any 
landscape,  and  by  this  rough  stadia  method  the  distance  can  be  approxi- 
mately measured.  The  switchboard  attendant  will  sometimes  find 
binoculars  useful  in  reading  the  instruments  on  a  direct-current  switch- 


LINE  CONSTRUCTION  AND  EQUIPMENT  33 

board  across  the  room  and  at  another  level,  ordinarily  entailing  a  trip 
downstairs. 

Battery  Search-lantern  for  Linemen. — The  overhead-line  trouble  de- 
partment of  the  Topeka  (Kan.)  Edison  Company  makes  good  use  of  a 
battery-operated  search-lantern  when  required  to  do  night  repair  work. 
A  regular  12-in.  automobile  search-lantern  is  employed  with  a  12-c.p., 
6- volt  tungsten  lamp.  The  lantern  is  pivoted  in  the  socket  of  the  3-ft. 
iron  tripod  which  was  built  in  a  local  blacksmith  shop.  With  its  double 
trunnions,  the  lantern  can  be  turned  and  held  in  any  position.  A  60- 
amp.-hour  ignition-type  storage  battery  supplies  energy  through  an  8-ft. 
length  of  flexible  cord.  This  battery  needs  to  be  charged  only  two  or 
three  times  a  month  and  is  always  kept  ready  to  be  placed  in  the  trouble 
wagon  with  the  lantern  for  emergency  use. 

Trouble  Man's  Portable  Search-lamp. — An  acetylene  gas  tank  and 
lamp  of  the  type  used  by  motorcyclists  makes  a  valuable  addition  to  the 
trouble-hunting  kit  of  the  Marion  (Ind.)  company's  line  department. 
For  $2  a  harness  maker  furnished  a  leather  carrying  case,  enabling  the 
tank  to  be  strapped  to  the  man's  back  out  of  his  way.  A  flexible  rubber 
hose  connects  the  tank  with  the  hand  lamp.  The  complete  equipment 
weighs  only  12  Ib.  and  costs  but  $10  to  116  for  the  tank,  $4  for  the  lamp 
and  $2  for  the  carrying  harness.  The  tank  can  be  exchanged  for  a  freshly 
charged  container  at  a  very  low  cost.  The  carrying  handle  for  the  lamp 
can  be  hooked  over  the  workman's  belt  if  desired,  or  one  man  can  be 
detailed  to  hold  the  lamp  on  the  ground  while  the  others  complete  the 
repairs.  This  outfit  is  especially  valuable  in  locating  pole  trouble,  fallen 
wires,  etc. 

Bucket  for  Bailing  Pole  Holes. — On  running  a  pole  line  through 
territory  which  was  rather  swampy,  considerable  difficulty  was  found 
in  keeping  water  out  of  the  holes  while  they  were  being  dug.  The  ordi- 
nary hand  pump  could  not  be  used  because  the  amount  of  water  necessary 
to  prime  the  pump  was  almost  as  much  as  the  water  in  the  hole,  and  it 
took  a  great  deal  of  time  to  pump  out.  Mr.  Schuster,  of  the  Cosmopolitan 
Power  Company,  Chicago,  in  charge  of  the  work,  devised  a  little  scheme 
which  seems  new.  A  heavy  galvanized  pail  was  taken  and  three  flat 
valves  from  an  ordinary  hand  pump  were  soldered  in  the  bottom  of  the 
pail.  All  that  is  necessary  to  pump  the  water  out  of  the  hole  is  to  push 
the  pail  down  into  the  hole,  which  opens  the  valves,  allowing  the  water 
to  run  in.  The  withdrawing  of  the  pail  closes  the  valves  and  the  water 
can  be  emptied  out. 

Blasting  Holes  for  Wooden  Poles  with  Dynamite. — Nearly  every 
central-station  manager  north  of  the  Mason  and  Dixon  line  has  had  the 
unpleasant  experience  of  paying  prices  ranging  upward  from  $1  apiece  for 
pole  holes  which  had  to  be  dug  in  frozen  ground.  The  accompanying 


34 


HANDBOOK  OF  ELECTRICAL  METHODS 


illustration  shows  the  scheme  which  was  used  by  the  Marion  Light  &  Heat- 
ing Company,  of  Marion,  Ind.,  for  digging  holes  when  the  ground  was 
frozen  to  a  depth  of  more  than  24  in.  The  hole  was  first  tapped  and  the 
earth  removed  to  a  depth  of  from  12  in.  to  15  in.,  care  being  taken  that 
the  top  of  the  hole  was  in  conformity  with  the  size  of  the  finished  hole 


Fuse 


I 

FIG.    1. BLASTING  HOLES  FOR  WOODEN  POLES  WITH  DYNAMITE. 


desired.  A  long-handled  auger  was  then  used  to  bore  a  hole  slightly  larger 
in  diameter  than  a  stick  of  dynamite  to  a  depth  of  about  27  in.  or  30  in. 
The  charge,  when  placed  in  this  small  hole  and  tamped  in  and  ignited, 
blew  a  neat  round  excavation  as  large  in  diameter  as  the  portion  which 
had  been  dug  out  at  the  top.  With  three-quarters  of  a  stick  of  dyna- 
mite at  the  depth  specified  in  the  illustration,  a  hole  5  ft.  deep  was 
secured  in  the  clay  ground  at  an  average  saving  of  15  to  20  per  cent, 
over  the  cost  of  manual  digging. 

Numbering  System  for  Pins  and  Cross-arms. — H.  I.  Ward,  electrical 
engineer  Muskogee  (Okla.)  Gas  &  Electric  Company,  has  arranged  a 
numbering  scheme  for  his  pins  and  cross-arms  as  follows :  On  all  poles  the 
pins  on  the  top  arm  are  numbered  as  "tens,"  those  on  the  second  arm  as 
"twenties,"  third,  "thirties,"  etc.  On  lines  running  north  and  south 
the  poles  are  numbered  from  east  to  west,  and  on  lines  running  east  and 
west  they  are  numbered  from  north  to  south.  Six-pin  arms  are  the  stand- 
ard although  some  four-pin  arms  are  used.  As  single-phase  and  arc 
circuits  precede  in  most  extensions,  these  take  the  top  arm.  On  all  lines 
running  north  and  south,  single-phase  primaries  take  the  two  east  pins 
and  are  numbered  11  and  12.  Since  only  one  arc  circuit  wire  is  run  on  a 
pole  line,  except  in  special  cases,  the  arc  wire  takes  the  pole  pin  on  the 


LINE  CONSTRUCTION  AND  EQUIPMENT 


35 


same  side  and  same  arm  as  the  single-phase  primaries,  and  is  No.  13. 
Three-phase  primaries  take  the  second  arm,  pins  Nos.  21,  22  and  23  being 
placed  on  the  same  side  as  the  single-phase  primaries.  When  single- 
phase  three-wire  and  three-phase  secondaries  are  run  they  take  the  oppo- 
site side  of  the  pole  and  the  same  arm  as  the  primaries  feeding  them. 
None  of  the  pins  are  actually  labeled,  of  course,  the  designation  shown 
being  simply  memorized  by  the  line  workers.  The  same  scheme  is  carried 
out  on  pole  lines  running  east  and  west,  all  high-tension  lines  being  placed 
on  the  north  side  of  the  poles.  An  application  of  this  method  is  shown 
in  Fig.  1. 


(L^w-Tension) 
West  or  South "*~ 


Secondaries 

Single-phase            Arc        Single-p 

Three  -wire^ 
@    ©     (fi) 

Dircuit^      Prima 
©     ©    © 

I 

| 

Three-phase 
—  Secondaries 

©     ©     © 

Three-phase 
Primaries    ~ 

i         -                                                      1 

—  ~  — 

(High-Tension) 
"^East  or  North 


FIG. 


-NUMBERING  SYSTEM  FOR  PINS  AND  CROSS-ARMS. 


Cross-arms  made  of  Old  Pipe. — On  all  new  construction  the  Marion 
(Ind.)  Light  &  Heating  Company  is  making  use  of  iron-pipe  cross-arms. 
The  second-hand  2-in.  gas-pipe  used  is  purchased  at  a  junk  value  of  3  cents 
a  foot  and  cut  into  5-ft.  cross-arm  lengths.  The  metal  pins  are  clamped 
to  the  pipe,  standard  wagon  clips  (costing  2  cents  each  complete  with 
nuts)  being  fitted  to  the  special  galvanized  pin  castings  produced  locally 
for  3  cents  each.  The  total  cost  of  each  pin  is  thus  5  cents.  Holes  are 
bored  for  the  pole  bolt  and  braces,  at  an  estimated  cost  of  1/2  cent  per 
pole,  including  handling.  The  brace  holes  are  made  90  deg.  from  the 
pole  bolt  hole,  and  the  braces  are  given  a  quarter  turn  at  their  arm  ends 
so  that  they  fit  under  the  bolt  heads.  This  is  believed  to  give  a  neater 
and  stronger  brace  construction,  although  it  is  not  clear  that  such  a 
quarter  turn  might  not  start  a  tendency  to  buckling  of  the  brace.  After 
the  pipe  cross-arm  has  been  drilled  and. fitted,  it  is  painted  inside  and 
out  by  dipping  into  a  preservative  color.  Such  pipe  arms  are  expected 
to  last  twenty  years  or  more,  at  the  cost  of  a  single  wood  arm,  saving  the 
labor  cost  of  replacement. 

When  lines  are  to  be  dead-ended  it  is  necessary  to  erect  a  double  pipe- 
arm  supporting  the  insulators  from  the  top  as  well  as  the  bottom.  Ball 
strain  insulators  with  stiff- wire  jumpers  may  also  be  used.  A  color 


36 


HANDBOOK  OF  ELECTRICAL  METHODS 


scheme  is  used  also  to  identify  wires  by  the  color  of  the  corresponding 
insulator.  Thus,  arc  lines  are  on  light-yellow  insulators  while  the  2300- 
volt  primaries  are  carried  on  dark-brown  insulators.  The  four-wire 
secondary  circuits  are  mounted  on  white  porcelain,  and  the  ground  wire  is 
mounted  on  white  porcelain  insulators. 

Replacing  Insulators  with  5o,ooo-volt  Line  "Hot."  (By  L.  R.  Sloan).— 
With  the  aid  of  a  special  conductor  clip  which  is  fixed  to  the  top  of  the 
glass  pin-type  insulators  used  to  make  temporary  repairs  on  some  of  the 
50,000-volt  lines  of  the  Butte  Electric  &  Power  Company  in  Montana, 


^^S$%$^^ 

FIG.    1. — CORNER  CONSTRUCTION  ON  50,000-VOLT  LINE  IN  MONTANA. 

defective  insulators  are  regularly  replaced  without  " killing"  the  line. 
Climbing  the  pole,  the  lineman  first  adjusts  a  temporary  strut  support 
under  the  wire  to  keep  it  from  falling  on  the  cross-arm  and  then  proceeds 
to  smash  the  defective  insulator  off  its  pin  with  a  long-handled  hammer 
ing  a  5-ft.  shank.  Holding  the  charged  conductor  out  of  the  way,  the 
new  insulator  is  dropped  into  place  on  the  pin.  The  wire  is  then  lifted 
into  the  clip  socket  on  the  top  of  the  insulator.  This  holds  it  fast  against 
slipping  off  the  insulator,  although,  of  course,  exerting  no  longitudinal  grip 
on  the  conductor  itself.  The  repair  is  effective,  however,  until  the  line 


LINE  CONSTRUCTION  AND  EQUIPMENT 


37 


can  be  " killed"  later  to  enable  the  lineman  to  tie  in  the  insulator  in  the 
regular  way. 

Corner  Construction  for  5o,ooo-volt  Line. — The  view,  Fig.  1  on 
page  36,  shows  the  unique  corner  construction  developed  by  the  engineers 
of  the  Butte  Electric  &  Power  Company's  system  for  use  on  some  of  the 
company's  50,000-volt  transmission  lines  in  southern  Montana.  These 
angle  turns  are  employed  in  conjunction  with  the  standard  wood-pole 
line  using  on  tangent  stretches  two  wood  cross-arms  and  three-part  sus- 
pension insulators.  The  upper  cross-arm  is  then  occupied  by  one  con- 
ductor and  the  ground  wire.  For  turns  like  that  shown,  all  wires  are 
brought  into  a  single  vertical  plane  and  are  supported  from  suspension  in- 
sulators carried  on  special  steel  triangle  brackets,  requiring  no  cross-arms. 
The  ground  wire  is  carried  around  the  outer  side  of  the  pole  at  turns,  and 
the  pole  itself  is  properly  guyed.  This  construction  has  now  become 
standard  for  making  all  turns  on  the  50,000-volt  lines  of  the  Butte  asso- 
ciated companies. 

Combination  Brace  and  Ground-wire  Bayonet  (By  W.  Llewellyn). — 
In  the  construction  of  a  new  transmission  line  entering  Calgary,  Alberta, 
Canada,  a  special  fitting  has  been  employed  which  takes  the  place  of  both 
the  ordinary  cross-arm  brace  and  iron  bayonet  for  ground-wire  support, 
besides  providing  a  balanced  arrangement  of  the  single- wire  cross-arm. 


C  B 


FIGS.    1  AND  2. COMBINATION  BRACE  AND  GROUND-WIRE  BAYONET. 


Fig.  1  shows  the  original  method  used  to  carry  the  upper  phase  wire  on  a 
separately  braced  cross-arm,  the  ground-wire  bayonet  being  bolted  to  the 
pole.  This,  of  course,  left  the  upper  arm  unbalanced.  When  the  new 
transmission  line  was  built,  paralleling  the  first  along  the  right-of-way  of 
the  Canadian  Pacific  Railroad,  the  construction  shown  in  Fig.  2  was 
adopted.  Here  the  brace  and  bayonet  are  made  from  a  single  bent  piece 
of  metal.  The  weight  of  the  ground-wire  approximates  that  of  the  phase- 
wire  and  serves  to  balance  it,  while  the  diagonal  brace  section  of  the 
support  is  required  merely  to  preserve  rigidity.  Cost  of  material  and 
work  of  installation  are  reduced. 


38  HANDBOOK  OF  ELECTRICAL  METHODS 

Methods  of  Splicing  Wires  and  Cables  (By  H.  V.  Talbot).—  Splices 
in  bare  copper  line  wire  can  be  made  as  indicated  in  Fig.  1  and  should  be 
mechanically  and  electrically  secure  before  solder  is  applied.  There 
should  be  at  least  five  turns  in  the  neck  (Fig.  1)  of  a  splice  to  insure  that 
the  unsoldered  splice  will  be  as  strong  as  the  wire  of  which  it  is  made.  All 
splices  in  wires  for  conveying  electricity  should  be  soldered  in  the  neck. 
It  is  not  always  necessary  to  solder  the  end  turns.  Mclntire  sleeves  are 

End  Turns  End  Turns 

—  H          K—  -  —  Neck  —  —  H         H- 


urns 


^-Untwisted  Sleev« 


Li  vo  Wire  Sleeve 


FIGS.    1  AND  2.  -  CONNECTIONS  IN  BARE  WIRE. 

very  satisfactory  and  are  used  to  a  great  extent  for  splicing  aerial  line 
wires.  (See  Fig.  2.)  Solder  is  not  necessary  where  sleeves  are  used. 
Splices  in  insulated  aerial  line  wires  are  made  similarly  to  that  shown  in 
Fig.  1,  except  that  tape  is  served  around  the  splice  for  insulation.  (See 
Fig.  3.)  If  the  line  wire  has  only  weatherproof  insulation,  friction  tape  is 
sufficient,  but  if  the  inner  insulation  is  rubber,  rubber  tape,  to  the  thick- 
ness of  the  inner  insulation,  should  be  applied  before  the  friction  tape  is 
served. 

^  Weather-proof  Insulation 


ving 


Insulation  Braid 

m»»».          1   A          Copper  Sleeve,         K 


Conductor 

FIGS.    3,  4  AND  5. CONNECTION  IN  WEATHERPROOF  AND  RUBBER-COVERED 

WIRE. 

In  preparing  the  conductor  ends,  about  1  in.  of  each  end  should  be 
bared  and  cleaned;  then,  with  a  very  sharp,  thin-bladed  knife,  the  insula- 
tion should  be  beveled  for  about  1  in.  as  one  would  sharpen  a  lead  pencil. 
The  conductor  joint  should  preferably  be  made  with  a  copper  sleeve, 
sweating  the  latter  on,  care  being  taken  to  clean  off  all  surplus  solder,  or 
if  the  connection  is  made  by  twisting  the  two  ends  together,  that  the 
ends  do  not  protrude.  The  bevels  and  conductor  should  then  be  covered 
with  a  thin  coat  of  a  pure  rubber  cement,  and  this  should  be  allowed  to 
"set." 


LINE  CONSTRUCTION  AND  EQUIPMENT 


39 


When  insulating  the  joint  a  strip  of  3/4-in.  pure  rubber  tape  6  in.  to 
8  in.  long  should  be  wrapped  spirally  around  the  joint,  beginning  at  the 
bevel  on  a  level  with  the  insulation  (A  in  Fig.  5)  and  continuing  to  the 
other  side  of  the  joint  as  far  as  the  high  point  of  the  bevel  (B  in  Fig.  5). 
The  operator  should  continue  to  wrap  to  and  fro  until  the  insulation  is 
built  up  slightly  thicker  than  the  regular  wall.  The  tape  must  be  put 
on  under  tension — say  stretched  to  about  half  its  width,  and  care  must  be 
taken  to  have  everything  perfectly  clean. 

To  vulcanize  the  joint  partially  heat  may  be  applied  evenly  from  a 
spirit  lamp,  a  lighted  match  or  the  hand  for  about  one  minute.  The 
joint  may  then  be  wrapped  with  two  layers  of  3/4-in.  friction  tape.  If 
the  wire  is  braided  or  taped,  the  braid  or  tape  should  be  cut  well  back  so 
that  there  are  no  loose  threads  overhanging  to  interfere  with  the  proper 
insulation  of  the  joint.  Should  the  friction  tape  become  slightly  set,  as 
it  sometimes  does  in  extreme  cold  weather,  a  gentle  heat  will  restore  it. 


Friction  Tape 


Rubber  Tape 


.Rubber  Covered  Wire 

'Friction  Tape 


Conductors 


Siplice  being 
made 


Solder  here 


Rubber  Tape 


^Completed  Splice 

Binding  Wire. 


FIGS.    G,   7,   8,  9  AND   10. SPLICES  IN  INTERIOR  WIRING. 

Splices  in  interior  wires  are  made  as  shown  in  Figs.  6,  7,  8,  9  and  10. 
Not  as  many  turns  are  necessary  in  the  neck  as  for  aerial  line  wires,  and 
all  splices  must  be  soldered.  Rubber  tape  to  the  thickness  of  the  rubber 
insulation  must  be  used  on  rubber-covered  wires  and  friction  tape  must  be 
served  over  the  rubber  to  hold  it  in  place.  The  so-called  " fixture  splice" 
(Figs.  7  and  8)  is  used  largely  by  telephone  men  and  in  wiring  fixtures.  It 
can  be  conveniently  used  sometimes  in  splicing  two  wires  that  must  be 
drawn  taut  in  the  splicing.  A  splice  in  wires  is  often  made  at  a  point 
between  two  supports  (cleats  or  knobs)  in  this  way.  The  duplex  wire 
splice  (Fig.  9)  is  often  used  by  telephone  men.  The  joints  should  always 
be  " broken";  that  is,  they  should  not  be  opposite  each  other.  In  con- 
duit work  where  duplex  wire  is  frequently  used  joints  are  not  permitted  by 
the  National  Electrical  Code  except  in  junction  boxes,  but  nevertheless 
they  are  occasionally  made  as  indicated  and  pulled  into  the  conduit. 


40 


HANDBOOK  OF  ELECTRICAL  METHODS 


Rubber  and  friction  tape  are  applied  to  each  in  the  same  way  as  to  the 
joint  in  a  single  wire,  and  then  the  pair  of  wires  should  be  served  with 
friction  tape.  Joints  should  always  be  taped  so  that  the  insulation  over 
the  joint  equals  that  over  the  rest  of  the  conductor. 

Taps  in  interior  wires  are  made  as  shown  in  Figs.  11  and  13.     The 
"knotted"  tap  has  the  advantage  that  the  tap  wire  cannot  untwist  from 


Tap  Wire 


,Main 
.Wire 


Binding  Wire 


FIGS.    11,   12,   13  AND   14. METHOD  OF  MAKING  TAPS  OFF  MAIN-LINE  WIRE. 

the  main  wire.  Tape  should  be  applied  as  in  the  case  of  splices.  The  tap 
for  small  aerial  wires  (Fig.  4)  is  made  by  giving  the  tap  wire  one  long 
complete  wrap  around  the  main  wire  and  then  four  short  turns.  Taps  for 
larger  aerial  wires  can  be  made  as  suggested  in  Fig.  12.  The  long  wrap 
gives  the  joint  a  certain  amount  of  flexibility  which  is  necessary  for 
aerial  work  where  the  wires  are  moved  by  the  wind.  The  tap  for  very 


'Insulation 


Outer  Braid 


^Insulation 


Insulation- 


* 


Stranded  Conductor 

FIGS.    15,   16,   17,   18  AND  19. — METHODS  OF  MAKING  SPLICES  AND  TAPS  IN 
STRANDED  CONDUCTORS. 

large    wires   (Fig.  14)  is  made  by  serving  a  binding  wire  about  bared 
portions  of  the  tap  and  main  wires  and  then  soldering  the  whole. 

Joints  in  cables  are  made  as  shown  in  Figs.  15,  16  and  17.  The  wireo 
composing  the  cable  should  be  spread  and  each  pulled  out  straight  and  the 
core  or  a  few  inner  wires  cut  away  so  that  the  splice  will  not  be  bulky. 
Then  the  two  cable  ends  should  be  abutted  as  shown  in  Fig.  15,  and  the 
wires  interwoven  in  groups  of  two  each  and  served  along  the  cable.  The 


LINE  CONSTRUCTION  AND  EQUIPMENT 


41 


joint  is  soldered  by  pouring,  with  a  ladle,  molten  solder  through  and  over 
it.  For  interior  work  a  short  joint  like  that  of  Fig.  16  is  frequently  used, 
but  in  aerial  work  a  longer  one,  like  that  of  Fig.  17,  is  preferred.  For  an 
aerial  joint  (Fig.  17)  a  length  of  about  16  in.  to  20  in.  is  bared  at  the  end 
of  each  cable  in  order  to  make  a  splice. 

Taps  in  cables  are  made  as  suggested  in  Figs.  18,  19  and  20.  Fig. 
18  shows  how  the  tap  wires  are  "fanned"  out  before  being  served  about 
the  main  conductor,  and  Fig.  19  shows  a  completed  tap  joint  for  interior 
work.  Fig.  20  shows  a  completed  tap  joint  in  an  aerial  cable.  Tap 
joints  in  cables  can  be  made  with  a  binding  wire  similarly  to  the  method  of 


-Main  Conductors 


Tap  Conductor* 


Covering- 


Conductor 


A  Wrong  Method 
Conductor 


B  Right  Method 


Enfi  Turns  End  Turns 

/  k Neck 


Three  Bolt  Clamp 


Sir1 
'Seven  Strand  Cable 


FIGS.    20,   21,   22  AND  23. JOINTS  IN  HEAVY  CONDUCTORS  AND  STEEL  CABLES 

METHODS  OP  REMOVING  INSULATION. 

Fig.  14.  When  a  joint  like  that  of  either  Fig.  19  or  Fig.  20  is  made  the 
entire  core  or  some  wires  should  be  cut  from  the  center  of  cable  so  that  the 
joint  will  not  be  bulky. 

In  making  any  joint  the  wire  ends  should  be  scraped  bright  with  the 
back  of^a  knife  blade,  sandpaper  or  emery  paper,  so  that  the  solder  will 
adhere  readily.  Insulation  should  be  cut  away  as  shown  at  B  (Fig.  21) 
rather  than  as  shows  at  A.  When  cut  as  at  A  the  wire  is  likely  to  be 
nicked  and  with  the  B  method  the  tape  can  be  served  more  neatly  about 
the  joint.  The  outer  braid  should  be  cut  well  back  from  the  joint  so  that 
stray  strands  from  it  cannot  be  taped  into  the  joint  and,  by  capillary 
attraction,  conduct  moisture  thereto. 

For  soldering  joints  a  non-corrosive  fluid  is  recommended;  solutions 
made  with  acids  should  be  avoided.  The  commercial  soldering  pastes 
and  sticks  give  good  satisfaction  in  cleaning  joints  to  be  soldered.  Joints 
in  small  wires  are  best  soldered  with  a  soldering  copper,  and  burning  of 
the  insulation  is  thereby  avoided.  An  alcohol  or  a  gasoline  torch  should 
be  used  on  medium-sized  joints,  while  on  the  larger  ones  it  is  most  con- 
venient to  employ  a  solder  pot  and  ladle. 

A  soldering  flux  removes  and  prevents  the  formation  of  an  oxide  during 
the  operation  of  soldering,  so  that  the  solder  will  flow  readily  and  unite 
firmly  the  members  to  be  joined.  For  copper  wires  the  following  solu- 


42 


HANDBOOK  OF  ELECTRICAL  METHODS 


tion  is  recommended  by  the  Underwriters:  Saturated  solution  of  zinc 
chloride,  five  parts;  alcohol,  four  parts,  and  glycerine,  one  part. 

Soldering  paste  or  stick  can  be  made  as  follows:  Melt  1  Ib.  of  tallow 
and  add  1  Ib.  of  common  olive  oil;  stir  in  8  oz.  of  powdered  rosin;  let  this 
boil  up  and  when  partially  cool  add,  stirring  constantly,  1/4  pint  of  water 
that  has  been  saturated  with  powdered  sal-ammoniac.  Stir  the  mixture 
constantly  until  cool.  By  adding  more  rosin  it  can  be  cast  into  sticks. 

Galvanized  iron  or  steel  wires  are  spliced  as  shown  in  Fig.  1,  and  five 
turns  are  necessary  in  the  neck  of  the  splice  to  insure  that  the  splice  shall 
be  as  strong  as  the  wire.  The  strength  of  an  unsoldered  joint  is  deter- 
mined by  the  number  of  turns  in  the  neck,  the  end  turns  having  but  little 
holding  power. 

Small  galvanized  steel  cables  are  joined  in  the  same  way  as  are  wires, 
as  shown  in  Fig.  22.  There  should  be  five  turns  in  the  neck,  as  with  wires, 
and  a  few  end  turns  to  finish  off  the  joint.  Soldering  is  unnecessary  for 
guy  wires.  Larger  cables  can  be  spliced  as  shown  in  Figs.  15  and  17,  or 
mechanical  clamps  can  be  used  instead,  as  shown  in  Fig.  23.  Sometimes 
it  is  necessary  to  use  several  clamps,  instead  of  one,  as  the  figure  shows,  in 
order  that  the  joint  may  be  as  strong  as  the  wire. 


'x  2  "x  %"  L    for  G  round  Wire 


Pole  Top  Dia.  * 


"    244—  l-l-'-O*- 


7K^*"!   *~J- 


.4x40ak 


l         Cross-Azm  [__ 


Flat  lion 


Vr 


Grounded 
Metallic  PI. 


V 

FIG.    1. HIGH-TENSION  CROSSING  WITH  PROTECTIVE  LOOP. 

High-tension  Crossing  Construction  with  Protective  Loop. — In  the 
sketch  (Fig.  1)  is  shown  the  6600- volt  overhead  crossing  construc- 
tion adopted  by  the  Dayton  Power  &  Light  Company,  of  Dayton, 
Ohio.  This  design  adheres  generally  to  standard  specifications  but  has 
the  added  safeguard  of  an  extra  loop  passing  over  a  pin-type  insulator  on 
the  upper  cross-arm.  As  initially  contructed  this  loop  is  free  of  all  other 
tension  than  that  imposed  by  its  own  weight,  but  if  an  insulator  of  the 
crossing  span  breaks  the  upper  insulator  at  once  comes  into  play  to  sup- 


LINE  CONSTRUCTION  AND  EQUIPMENT  43 

port  the  line  both  mechanically  and  electrically.  This  eliminates  possi- 
bility of  the  power  line  falling  and  endangering  lives. 

For  railroad  crossings  this  extra-loop  construction  is  employed  on  the 
poles  at  each  end  of  the  90-ft.  crossing  span.  A  minimum  height  of  30 
ft.  is  imposed  from  track  rails  to  the  lowest  wire.  The  adjacent  135-ft. 
spans  are  also  double  guyed  with  5/16-in.  stranded-steel  cable,  each  pole 
top  being  tied  to  the  adjoining  pole  butt.  For  a  single-circuit,  three- 
phase  line,  as  shown,  all  conductors  are  mounted  in  the  same  horizontal 
plane  on  four-pin  arms.  The  lower  arm  is  of  4-in.  by  4-in.  oak,  capped  with 
a  1/8-in.  metallic  ground  plate,  while  the  upper  arm,  on  which  the  emer- 
gency loop  insulators  are  mounted,  is  of  3-in.  by  4-in.  by  0.25-in.  angle 
section.  Anchoring  the  upper  arm  rigidly  to  the  lower  is  a  pair  of  vertical, 
flat  1.125-in.  by  0.25-in.  braces,  which  also  serve  as  ground  connections. 

Another  form  of  crossing  construction  reported  from  Ohio  by  the 
electrical  transmission  committee  of  the  Ohio  Electric  Light  Association 
involves  a  reversed  catenary  arrangement.  The  regular  catenary  con- 
struction— that  is,  a  suspension  cable  with  loops  down  to  support  the  feed 
wire — was  considered  objectionable,  because  some  difference  of  potential 
through  leaks  might  set  up  rapid  depreciation. 

The  plan  adopted  was  the  extension  of  the  main  feeder  straight 
through  over  the  crossings  the  same  as  in  the  other  part  of  the  line  (ex- 
cept for  the  addition  of  the  double  arming  on  either  side  of  the  crossing) 
and  on  this  main  feeder  over  the  space  to  be  protected  loops  were  connected 
permanently  to  the  main  line  every  5  ft.  The  loop  wire  was  of  the  same 
size  copper  as  the  feeder.  The  loops  were  allowed  to  extend  down  about 
4  in.  below  the  feeder,  then  through  these  loops  another  copper  wire  of  the 
same  size  and  capacity  as  the  feeder  was  run.  This  wire  was  allowed  to 
hang  free  in  the  loops,  and  extended  to  and  beyond  the  insulator  supporting 
the  feeder  on  either  side  of  the  space  to  be  protected,  where  the  free  wire 
is  connected  to  the  feeder  with  a  good  soldered  joint.  Should  the  feeder 
break  from  any  cause  the  free  wire  will  then  support  the  feeder  and  prevent 
it  from  coming  down  or  doing  any  damage  to  the  crossing,  while  at  the 
same  time  continuity  of  service  will  be  unimpaired. 

Simple  Method  of  Transposing  Wires  (By  P.  F.  Lamed). — Fig.  1 
shows  a  scheme  of  transposing  a  pair  of  telephone  wires  at  every  pole  of 
the  transmission  line  along  which  they  are  carried.  This  is  certainly  so 
simple  as  to  have  deserved  better  attention  from  engineers  who  design 
lines  and  use  instead  the  unsatisfactory  double-groove  transposition  insu- 
lator or  four-insulator  construction.  The  method  consists  in  rotating  the 
circuit  by  crossing  wires  between  poles,  allowing  the  lower  wire  several 
feet  more  sag  than  the  other.  In  a  line  carried  on  pins  3  ft.  apart  and 
hung  in  600-ft.  spans,  3  ft.  difference  in  the  sags  of  the  crossing  wires  has 
proved  an  entirely  satisfactory  and  permanent  construction.  The  wires 


44 


HANDBOOK  OF  ELECTRICAL  METHODS 


cannot  swing  together  and  make  contact,  for  at  the  middle  of  the  span, 
where  the  tendency  to  swing  is  greatest,  the  wires  are  correspondingly 
most  widely  separated.  In  a  line  of  any  length  the  unsymmetrical  sus- 
pension of  the  wires  is  compensated  since  each  wire  occupies  alternately 
the  long  and  short  sag  position.  The  only  provision  to  be  made  in  using 
this  construction  is  that  the  wires  do  not  slip  on  the  insulators  or  the  latter 
rotate  under  the  unbalancing  action  of  the  unequal  spans,  letting  the  wires 
get  together. 


FIG.     1. SIMPLE  METHOD  OF  TRANSPOSING  WIRES. 

Use  of  Choke  Coils  with  Pole  Arresters  (By  L.  F.  Bradley). — Choke 
coils  are  inserted  in  the  2300-volt  lines  of  the  San  Antonio  (Tex.)  Gas  & 
Electric  Company  (Fig.  1)  on  the  station  side  of  each  lightning  arrester  to 
divert  abnormal  discharges  and  surges  into  the  ground  paths  and  away 
from  the  adjoining  sections  of  the  line.  These  choke  coils  are  made  up  of 
twenty-eight  turns  of  the  regular  line  conductor  wound  with  an  8-in.  in- 
ternal diameter,  the  wire  being  pyramided  so  that  the  coils  are  triangular 
in  section.  The  whole  is  then  tightly  wrapped  with  tape  and  mounted 
from  a  glass  insulator  on  a  bracket  pin  extending  from  the  cross-arm.  On 


To  Station 


28  Turns 


FIG.    1. CHOKE  COIL  INSERTED  IN  2300-VOLT  TRANSMISSION  LINE. 

the  longer  runs  these  choke  coils  are  inserted  at  intervals  of  about  1  mile  or 
wherever  arresters  are  installed.  Similar  coils  are  installed  at  the  under- 
ground cable  entries  of  all  overhead  lines.  More  than  fifty  of  these  coils 
were  in  use  on  the  San  Antonio  lines  in  May,  1912,  and  since  they  were 
put  in  lightning  troubles  have  noticeably  decreased,  according  to  G.  B. 
Cushman,  electrical  superintendent  of  the  company.  Occasionally  a  coil 
is  burned  out,  but  when  this  happens  it  can  be  easily  replaced. 

Adaptation  of  Three-phase  Arrester  for  Two-phase  Use. — In  pur- 
chasing  lightning-arrester   equipment  for   some   two-phase   circuits   in 


LINE  CONSTRUCTION  AND  EQUIPMENT 


45 


several  Kansas  City  substations  which  were  likely  to  be  changed  to  three- 
phase  operation  shortly,  standard  three-phase,  2300-volt  aluminum-cell 
arresters  were  selected  and  adapted  temporarily  to  two-phase  operation 
as  shown.  For  this  two-phase  protection  the  three-phase  equipment, 
it  will  be  noted,  required  only  four  elements  instead  of  the  six  generally 
furnished.  By  the  use  of  the  connections  shown  both  arresters  are 
charged  from  a  single  phase,  only  one  of  the  second-phase  terminals  being 
led  to  the  arrester.  This  unconnected  side  and  the  corresponding  side 
of  the  first  phase  are  equipped  with  feeder  regulators,  the  static  arresters 
of  which  afford  ample  protection. 


Phase  No.l 


Phase  No.2 


Normal 


Ground 


FIG.     1. — ADAPTATION  OF  THREE-PHASE  ARRESTER  FOR  TWO-PHASE  USE. 


As  furnished  by  the  manufacturer,  the  arrester  comprised  four 
groups  of  elements  connected  to  a  common  point,  with  the  far  side  of  one 
of  the  groups  grounded  onto  the  cell.  By  removing  one  jumper  the 
various  group  taps  were  made  available  for  two-phase  operation.  With 
the  charging-switch  blades  in  the  lower  position  both  phases  are  con- 
nected through  the  cell  to  earth.  With  the  switch  up  energy  is  taken 
from  the  first  phase  for  charging  both  sets  of  arrester  elements.  This 
arrangement  was  devised  by  R.  K.  McMaster,  electrical  engineer  of 
the  Kansas  City  Electric  Light  Company. 

Maintenance  of  Electrolytic  Arresters  (By  W.  W.  McCullough).— 
The  value  of  the  aluminum-cell  electrolytic  lightning  arrester  depends 
upon  the  proper  maintenance  of  the  film  on  the  surface  of  the  plates  mak- 
ing up  the  arrester.  The  maintenance  of  this  film  depends,  first,  on  the 
temperature  of  the  electrolyte,  and,  second,  on  the  frequency  of  "  flash- 


46 


HANDBOOK  OF  ELECTRICAL  METHODS 


ing"  or  "charging."  The  operation  of  electrolytic  arresters,  given  proper 
"  charging/'  presents  very  little  difficulty  in  climates  where  the  electrolyte 
is  not  subjected  for  long  periods  of  time  to  high  temperatures.  In  semi- 
tropical  countries  with  the  arrester  tanks  exposed  to  the  sun,  however, 
it  is  extremely  hard  to  keep  up  the  film  on  the  plates,  only  a  few  hours 
being  sufficient  to  dissolve  the  film  immersed  in  the  warm  electrolyte. 
This  trouble  has  been  remedied  to  a  large  extent  on  a  60,000-volt  system 
in  Florida  by  painting  the  arrester  tanks  white  instead  of  black  as  origi- 
nally furnished,  advantage  being  taken  of  the  increased  heat-reflecting 
qualities  of  a  white  surface  as  compared  with  a  black  one. 

Emergency  Strain  Insulators  Made  from  Glass  Insulators  (By  H.  L. 
Beardsley). — A  strain  insulator  that  gives  entirely  satisfactory  service 
when  used  with  ordinary  good  judgment  can  be  made,  as  indicated  in 


Right  Hand 

*-GIve  a  Downward 
Blow  with  Screw 
Driver 


FIG.    1. METHOD     OF 

ALTERING  INSULATOR. 


Su 


FIG.    2. ALTERED  INSU- 
LATOR IN  USE. 


Drip  Loop 

FIG.    3. LINE    WIRING 

FOR  A  MOTOR. 


Fig.  1,  by  knocking  the  end  out  of  a  commercial  glass  insulator.  Ob- 
viously a  strain  insulator  made  in  this  way  is  not  as  good  either  mechan- 
ically or  electrically  as  many  standard  types  that  are  readily  obtainable. 
It  is  recommended  only  for  emergencies  or  temporary  installations. 
Some  applications  are  shown  in  Figs.  2  to  7. 

Any  heavy  tool  having  a  portion  of  suitable  diameter  and  long  enough 
to  reach  and  enter  the  bottom  of  the  glass  insulator  may  be  used  for 
altering  the  insulator  instead  of  the  screw-driver  shown  in  Fig.  1.  The 
insulator  to  be  altered  is  held  with  the  left  hand  and  with  the  tool  a  sharp 
downward  blow  is  given  into  the  threaded  cavity  of  the  insulator  and 
against  the  bottom.  Occasionally  the  insulator  will  break  into  many 
pieces  and  be  lost,  but  usually  only  its  top  is  cracked  off  on  a  reasonably 
regular  plane.  Linemen  use  their  connectors  or  their  pliers  in  altering 
insulators.  The  blow  is  given  with  one  of  the  legs  or  sides  of  either  of  the 
tools. 

Fig.  2  shows  one  of  the  many  methods  of  making  up  the  wires  about 
an  altered  glass  insulator.  In  the  illustration  the  line  wire  is  shown  in 
the  groove  and  the  supporting  or  pull-over  wire  is  shown  threading 
through  the  hole.  This  arrangement  need  not  necessarily  be  followed. 


LINE  CONSTRUCTON  AND  EQUIPMENT 


47 


The  relative  locations  of  the  two  wires  are  often  made  the  opposite  of 
those  shown.  In  Fig.  3  an  application  is  shown  of  the  combination 
detailed  in  Fig.  2.  A  motor  had  been  installed  for  a  contractor's  plant 
in  a  shed  (Fig.  3)  which  was  close  to  a  railway  trestle.  It  was  imperative 
that  the  motor  should  be  connected  immediately  to  conductors  on  a  pole 
line  a  short  distance,  possibly  150  ft.,  away.  Wire  and  insulators  were 
available,  but  no  other  electrical  material  and  it  was  desirable  so  to  make 


Entrance 
Tube 


FIG.    4. AN  EMERGENCY  APPLICATION  OF 

ALTERED  INSULATOR. 


FIG.    5.- 


-AN  IMPROVISED  TREE 
INSULATOR. 


the  installation  that  it  would  be  reliable  and  capable  of  operating  for 
several  months.  The  outside  wiring  was  insulated  and  supported  with 
altered  insulators  as  suggested  in  Fig.  3. 

Another  emergency  application  is  shown  in  Fig.  4.  In  this  case 
altered  insulators  were  used  to  restore  electric  lighting  service  to  a  build- 
ing. When  the  electric  lighting  company's  emergency  man  arrived  at 
the  building  he  found  that  the  pole  from  which  the  service  wires  to  the 


Polei 

I  c  / 

Mr.Smith'a 

w  xx 

X^ 

•N    Property 

X 

\        Orginal 

roperty 
Line 

f 

Altered 
Insulators 

N\     Position 
\*  —  •  of  Line 
\        Wire 

/ 

Bee  Fig.4  foiy 

\ 

x' 

Details      xk 

2 

2 

Pole  A 


Curb  Line       Pole  B 
Exe  Street 

FIG.    G. SOLUTION  OF  A  RIGHT-OF- 
WAY   DIFFICULTY. 


FIG.  7. — PLAN  VIEW  OF  INSULATOR 
ARRANGEMENT. 


building  were  taken  had  been  pulled  partially  over  through  the  breaking 
of  a  guy  wire,  that  the  service  wires  had  been  broken,  and  that  the  iron 
brackets  and  the  wooden  cleat  which  supported  them  had  been  pulled 
down.  It  was  impossible  to  replace  the  cleat  and  bracket  with  the  tools 
the  man  had  and  he  could  not  pull  the  pole  back  into  normal  position,  so 
he  restored  service  temporarily  by  driving  spikes  at  the  corner  of  the 


48  HANDBOOK  OF  ELECTRICAL  METHODS 

building  and  supporting  the  service  wires  on  the  spikes  with  altered  insu- 
lators as  shown  in  Fig.  4. 

Altered  insulators  can  be  used  for  tree  insulators  as  suggested  in 
Fig.  5.  Where  a  line  wire  is  in  contact  with  the  limb  or  branch  of  a  tree 
it  is  usually  possible  to  eliminate  the  contact  by  placing  the  line  wire  in 
the  groove  of  an  altered  insulator  and  pulling  and  tying  it  away  from  the 
offending  member  with  a  pull-over  wire  as  may  be  seen  in  Fig.  5.  The 
line  wire  is  sometimes  tied  in  the  groove  of  the  insulator,  but,  as  a  rule, 
this  is  not  desirable  because  if  the  line  wire  is  tied  the  swaying  of  the  tree 
may  break  the  conductor.  Tree  insulators  specially  formed  from  glass 
or  porcelain  are  made  and  are  preferable  for  permanent  work  to  the  altered 
type  of  Fig.  5. 

A  right-of-way  difficulty  was  solved  with  altered  insulators  in  the 
instance  pictured  in  Fig.  6.  Wires  of  a  series  circuit  spanned,  as  shown  by 
dotted  lines,  from  poles  A  and  B  to  pole  C  and  one  of  them  crossed  prop- 
erty. To  the  presence  of  this  wire  the  owner  objected  and  insisted  that  it 
be  removed.  The  heavy  lines  show  how  the  wires  were  rearranged  to 
meet  the  property  owner's  demands  without  setting  a  pole,  Fig.  7  shows 
the  arrangement  used  and  the  wiring  of  the  altered  insulators.  The  wir- 
ing was  made  up  on  the  ground,  after  careful  measurements  had  been  taken, 
and  was  then  raised  to  its  aerial  position  before  the  original  wires,  shown 
by  the  dotted  lines,  were  removed.  The  new  work  was  then  spliced  to  the 
portion  of  the  old  that  was  to  remain  and  the  useless  part  of  the  old  instal- 
lation was  cut  down. 

Concrete  Poles  Integral  with  Building  to  Save  Space. — At  the  No.  3 
plant  of  the  Aluminum  Company  of  America  at  Niagara  Falls,  N.  Y., 
the  problem  of  conserving  real  estate  has  been  solved  in  one  instance  by 
resorting  to  a  novel  type  of  overhead-line  construction.  The  motor- 
service  wires  reach  the  mill  over  a  pole  line  and  from  the  corner  of  the  low 
concrete  building  which  adjoins  the  main  factory  are  carried  by  concrete 
poles  constructed  integral  with  the  building.  As  shown  in  the  upper,  Fig. 
1,  page  49,  the  reinforcing  extends  up  the  wall  of  the  building  and  con- 
tinues to  a  point  near  the  top  of  the  pole.  Braces  of  reinforced  concrete 
are  set  on  three  sides  of  the  poles  at  an  angle  of  about  45  deg.  The  poles 
extend  about  10  ft.  above  the  roof,  giving  ample  clearance  between  the 
wires  on  the  lower  cross-arm  and  the  roof.  This  arrangement  has  the 
further  advantage  of  allowing  the  spur  track  which  is  shown  beside  the 
wall  to  be  placed  closer  to  the  factory  than  would  have  been  possible  if 
wooden  poles  had  been  set  in  the  earth  near  the  building.  Thus  in  loading 
and  unloading  cars  the  distance  between  the  car  door  and  the  sill  of  the 
factory  entrance  is  reduced  to  a  few  inches. 

Temporary  Cross-arm  Braces  to  Aid  Construction  Crews. — Quanti- 
ties of  strong  and  vivid  language  are  often  wasted  by  the  foremen  of  line 


LINE  CONSTRUCTION  AND  EQUIPMENT 

/\ 


Conductors 

Cross- Arms 


9      9 


Concrete  Braces^ 


9      Q 


Concrete 
Pole 


Minimum 
Clearance 


FIG.    1. CONCRETE  POLE  INTEGRAL  WITH  BUILDING  TO  SAVE  SPACE. 


I 


Il 


•ti B tt-71 


Cross-Arm^ 


Pole 


-b b 


Bolt' 


II  l|  II         I    O     I         H  '! 

* b ii     Li  1 1  i ml     It b- 


8 a 


x  Selected  Cross-Arms  or 
~\  other  Suitable  Timber 


4i U 


49 


FIG.    1. — TEMPORARY  CROSS-ARM  BRACES  TO  AID  CONSTRUCTION  CREWS. 


50 


HANDBOOK  OF  ELECTRICAL  METHODS 


gangs  when  they  find  that  the  cross-arms  on  a  pole  which  has  been  used 
by  the  men  for  a  " resting  place"  while  pulling  wires,  splicing  and  testing 
are  out  of  line  when  the  job  is  finished.  An  Ohio  foreman  is  saving 
much  of  his  formerly  wasted  energy  by  resorting  to  the  expedient  shown  in 
the  lower  Fig.  1,  page  49.  A  set  of  cross-arms  of  straight  2-in.  by 
4-in.  pine  timbers  properly  bored  and  fitted  with  bolts  is  carried  as  part  of 
the  construction  equipment,  and  when  it  is  necessary  for  several  men  to 
work  on  a  pole  for  any  considerable  length  of  time  the  temporary  braces 
are  used  to  hold  the  arms  in  place.  Ordinary  0.25-in.  space  bolts  are 
found  satisfactory  for  holding  the  braces  to  the  arms.  In  work  of  recon- 
struction where  the  old  cross-arms  and  poles  are  rotted  at  the  gains  this 
brace  is  also  useful. 

Operating    Results    with    a    2300-volt    Single-wire    Ground-return 
Transmission   Line. — In   April,    1913,   the   Benton   Harbor-St.    Joseph 


WVWW — TTI 

(L.A.)  GL 


Ground 

r 

Projected  2300|V.Single-Wirt>  Ground-Ret. 


Phased 


Line      (L.A.) 


FIG.    1. A  2300-VOLT  SINGLE-WIRE  GROUND  RETURN  TRANSMISSION  LINE. 

(Mich.)  Railway  &  Light  Company  began  the  construction  of  a  2300- 
volt  single-wire  ground-return  transmission  line.  Regular  service  began 
June  1  For  the  purpose  of  the  severest  possible  test,  this  single- wire 
grounded  line  was  built  under  the  most  adverse  conditions  that  such  a 
line  could  be  expected  to  meet.  A  telephone  company  already  had  a  line 
of  poles  along  the  route,  carrying  a  rural-line  circuit  of  two  wires  on 
brackets.  Permission  was  obtained  to  reconstruct  this  line  by  placing  a 
standard  5-ft.  four-pin  cross-arm  in  the  top  gain  of  these  25-ft.  poles, 
transferring  the  telephone  wires  to  two  pins  on  one  side  of  the  arm  and 
running  the  2300-volt  wire  on  the  outer  pin  at  the  far  side.  The  single- 
wire  line  thus  built  is  approximately  2.5  miles  long.  Triple-braided 


LINE  CONSTRUCTION  AND  EQUIPMENT  51 

weatherproof  wire  was  used  throughout  for  both  primaries  and  secon- 
daries. Owing  to  delay  in  securing  the  one-to-one  transformers  desired 
for  connecting  the  ground-return  line  with  the  company's  ungrounded 
system,  a  pair  of  standard  distribution  transformers  were  utilized,  their 
secondaries  being  connected  together  to  take  the  place  of  the  one-to-one 
units. 

Customers'  secondaries  (see  Fig.  1),  are  not  grounded,  and  all 
possible  effort  is  made  to  prevent  such  grounding.  Lightning  arresters 
are  installed  at  every  transformer.  Transformers  are  fused  between 
terminal  and  ground  and  between  the  primary  wire  and  ground.  Both 
secondary  and  transformer  construction  is  of  the  company's  standard 
type,  the  second  or  grounded  wire  of  the  primary  being  run  to  a  No.  4 
rubber-covered  conductor,  which  is  nailed  to  the  pole  and  covered  with 
special  wood  molding.  This  ground  wire  connects  with  both  a  24-in. 
copper  ground-cone  buried  in  moist  earth,  with  one  sack  of  charcoal 
around  the  cone,  and  a  0.75-in.  galvanized  ground-pipe  driven  deep  into 
the  earth  at  the  base  of  the  pole.  In  some  cases  it  was  necessary  to  go 
back  two  or  three  poles  to  find  lowrer  ground  which  would  retain  moisture 
better. 

Leaving  the  main  transformers,  at  the  end  of  the  first  five  poles,  it 
became  necessary  to  cross  a  millpond  with  a  575-ft.  span.  This  was  done 
with  a  single  messenger  and  two  No.  8  triple-braided  weather-proof  wires 
carried  on  a  specially  insulated  hanger  so  arranged  that  if  necessary 
the  entire  span  could  be  drawn  in  at  either  end  and  any  necessary  repairs 
made  directly  from  the  pole.  Two  wires  were  carried  across  this  mill- 
pond  in  the  expectation  that  a  little  later  the  second  phase  might  be  run 
out  on  another  circuit,  thus  assisting  in  balancing  the  system. 

When  first  starting  a  great  deal  of  trouble  was  experienced  with 
induction  on  the  telephone  lines.  Finally  the  telephone  wires  were  trans- 
posed every  fifth  pole,  using  standard  Michigan  Telephone  Company 
transpositions.  This  helped  the  matter,  but  there  was  still  considerable 
noise  caused  by  grounds  where  the  primary  line  ran  through  trees,  some 
sections  of  the  line  traversing  heavy  maple,  elm  and  willow  shade  trees. 
This  trouble  was  only  partly  cleared  up  before  the  men  were  called  away. 
After  the  line  had  gone  through  several  severe  electrical  storms  the  men 
were  again  put  on  the  line,  thoroughly  clearing  it  of  all  tree  grounds,  etc. 
While  there  is  still  a  slight  buzzing,  caused  by  induction  and  noticeable 
when  using  the  rural  telephone,  it  cannot  be  detected  at  the  other  end 
of  the  line  and  the  voice  transmission  is  perfectly  clear  and  normal. 
Not  a  single  fuse  on  this  line  has  been  put  out  by  lightning,  either  on  the 
transformers  or  in  residences.  At  the  time  of  writing,  there  were  no 
motors  on  the  line. 

The  company  is  thoroughly  satisfied  that  with  a  properly  constructed 


52  HANDBOOK  OF  ELECTRICAL  METHODS 

pole  line  on  a  private  right-of-way,  avoiding  heavy  trees  such  as  shade 
many  rural  highways,  single-wire  lines  can  be  built  much  more  cheaply 
than  the  standard  two-wire  construction  and  with  less  danger  from  high 
winds,  sleet  and  other  line  troubles.  A  line  of  this  character  using  25-ft. 
poles  with  5-in.  tops  costs  about  $228.65  per  mile  as  itemized  in  this  table: 

Thirty-five  25-ft.  poles  (5-in.  tops),  at  $2 . 50 $87 . 50 

Five  35-ft.  poles,  at  $3 . 65 18.25 

Thirty-five  wood  brackets,  at  2  cents 0 . 70 

Five  four-pin  cross-arms,  at  40  cents 2 . 00 

Twenty  wood  pins,  at  2  cents 0 . 40 

Forty  glasses,  at  2  cents 0 . 80 

Bolts,  lags,  etc 1 . 00 

400  Ib.  No.  8  triple-braided  weatherproof  wire,  at  17  cents. ..  .  68.00 

Labor..  50.00 


Total $228.65 

A  line  of  equivalent  capacity  constructed  of  the  same  material,  but 
employing  the  usual  two  wires  instead  of  one,  would  cost  $380.30  per 
mile,  a  difference  of  $151.65  per  mile.  It  will  be  noted  in  the  above 
tabulation  that  no  estimate  has  been  made  for  the  necessary  amount  of 
two-wire  line  where  transformers  were  installed,  nor  for  the  grounding  of 
transformers.  The  latter  costs  about  $5  per  transformer. 

Changing  35,ooo-volt  Insulators  on  Live  Circuits. — To  change  insu- 
lators on  a  35,000-volt  transmission  line  while  several  large  glass  factories 
are  taking  energy  from  the  line  is  rather  an  uncommon  feat.  Such  work 
was,  however,  performed  by  a  lineman  of  the  Marion  (Ind.)  Light  &  Heating 
Company  on  one  of  its  transmission  lines  not  far  from  the  city  limits. 
A  common  hand-axe  handle  made  into  a  wrench  and  insulated  with  four 
thicknesses  of  varnished  cambric  held  in  place  with  friction  tape  was 
used  to  free  the  line  from  the  insulator.  The  handlines  used  in  the 
operation  were  baked  over  night  in  an  oven  to  drive  out  all  moisture. 
In  a  very  short  time  the  broken  insulator  was  removed  and  a  new  one 
put  in  its  place.  The  fact  that  the  wishbone  cross-arms  on  the  line  were 
all  grounded  made  the  feat  an  exceptionally  perilous  one. 

Concrete  Resistors  for  Lightning  Arresters. — Concrete  resistors  for 
lightning-arrester  service  which  are  in  general  use  on  the  11, 000- volt 
and  22,000-volt  systems  of  a  Georgia  central-station  company  are 
shown  in  Fig.  1.  page  59.  Into  a  solid  concrete  block  measuring 
approximately  4  ft.  long  and  1  ft.  on  a  side  are  cast  two  squares  of 
bronze  or  copper  mesh,  one  near  each  end.  The  block  is  then  stood 
upright  at  the  point  of  installation,  being  set  a  few  inches  into  the  earth 
to  insure  it  against  accidental  overturning.  To  the  upper-mesh  electrode 
is  connected  the  tap  from  the  middle  member  of  the  double  horn-gap,  the 
circuit  through  to  the  transformer  or  other  station  apparatus  being 


LINE  CONSTRUCTION  AND  EQUIPMENT 


53 


completed  by  a  piece  of  copper-wire  fuse,  as  shown.  The  lower-mesh 
electrode  imbedded  in  the  block  is  similarly  connected  to  a  couple  of  8-ft. 
ground  pipes  or  ground  rods  driven  deep  into  the  soil.  While  the  circuits 
are  also  adequately  protected  on  the  low-tension  side,  the  fuse  shown  is 
especially  provided  for  protection  to  the  high-tension  line.  The  copper- 
wire  link  used  is  designed  to  give  four  times  the  full-load  carrying  capacity 
and  each  lineman  carries  in  his  pocket  notebook  a  table  of  sizes  suitable 
for  the  various  installation  ratings  at  both  11,000  volts  and  22,000  volts. 


Transformer 


Bronze  Mesh-- 


Bronze  Mesh 


8  ft. Ground  Pipe 


FIG.     1. CONCRETE  RESISTORS  FOR  LIGHTNING  ARRESTERS. 

Raising  the  Height  of  Old  Inclosed-Arc  Lamp-Posts  at  Cincinnati, 
Ohio. — The  large  number  of  inclosed-arc  lamps  which  formerly  lighted 
the  streets  of  Cincinnati,  Ohio,  were  replaced,  late  in  1913,  with  6000 
4-amp.  magnetite  units,  but  the  new  high-powered  illuminants  when 
hung  from  the  posts  which  carried  the  older  lamps  were  found  to  give 
trouble  and  even  discomfort  from  glare  in  the  eyes  of  passers-by.  This 
difficulty  had  not  been  apparent  with  the  former  low-powered  units, 
but  became  so  critical  with  the  initial  trial  installations  of  the  magnetite 
lamps  that  it  was  found  necessary  to  raise  the  posts  by  about  7  ft.  6  in. 
and  so  increase  the  visual  angle. 

The  sketches  herewith  show  how  this  change  was. accomplished  by 
first  sawing  in  two  the  old  shanks  and  then  socketing  these  stumps  into 
pieces  of  4-in.  pipe,  10  ft.  10  in.  in  length.  The  original  standards  were 
of  3-in.  pipe,  which  was  found  to  fit  snugly  inside  the  4-in.  extension 


54 


HANDBOOK  OF  ELECTRICAL  METHODS 


piece.  An  ornamental  cap  was  added  at  the  top  of  the  extension  to  make 
a  neat-fitting  joint.  Above  this  point  the  old  poles  were  tapered  into 
2.5-in.  pipe,  and  again  to  2-in.  pipe  to  form  the  curved  neck. 

The  reconstructed  poles  place  the  point  of  lamp  suspension  at  a  height 
of  21.6  ft.  above  the  pavement  level,  bringing  the  arc  itself  at  a  height 


2X  Pipe   (Old  Pole) 


3  Pipe  (Old  Pole) 


4  Pipe  (New  Pole) 


3  Pipe  (Old  Pole) 


Street  Level 


FIGS.    1  AND  2. RAISING  THE  HEIGHT  OF  OLD  ENCLOSED  ARC-LAMP  POSTS  AT 

CINCINNATI,  OHIO. 

of  about  18  ft.,  well  out  of  the  way  of  direct  vision.  Figs.  1  and  2 
show  respectively  the  sectional  construction  of  the  rehabilitated  posts 
and  their  appearance  when  the  work  of  raising  and  reconstructing  them 
had  been  completed. 


LINE  CONSTRUCTION  AND  EQUIPMENT 


55 


Support  of  Long  Transmission  Span  by  Messenger  Cable. — After  the 
completion  of  the  Eastern  Michigan  Edison  Company's  hydroelectric 
plant  at  Ann  Arbor,  Mich.,  an  unexpected  market  for  energy  opened  up 
in  two  towns,  to  the  north  and  west  respectively.  To  transmit  energy 
to  the  latter  place  by  the  shortest  practicable  route,  it  was  necessary  to 
string  the  23,000-volt  conductors  across  the  pond  above  the  dam,  requir- 
ing a  span  of  about  1000  ft.  Figured  for  tension,  No.  0  hard-drawn 
copper  wire  was  found  to  have  just  sufficient  strength  to  be  used  safely  on 
this  span.  However,  while  a  jumper  from  the  station  high-tension  bus 
was  being  soldered  onto  one  of  the  span  wires  the  heat  of  the  solder 
annealed  the  hard-drawn  copper,  so  far  reducing  its  strength  that  the 
conductor  broke  under  its  own  tension.  To  avoid  using  the  larger  wire 
needed  to  withstand  the  tension,  the  construction  shown  in  Fig.  1  was 


30,000-Volt 
Dead-End  Insulator 


Shaped  Dead-End  Tower 

45JFt.  High 
FIG.    1. SUPPORT   OF    LONG    TRANSMISSION   SPAN  BY   MESSENGER   CABLE. 

then  adopted.  H-shaped  wooden  frames  were  built  and  erected  on  each 
side  of  the  pond  as  dead-end  towers.  Back  of  each  on  its  land  side 
another  H-shaped  frame  was  erected  to  help  withstand  the  horizontal 
pull  of  the  long  span. 

The  main  dead-end  towers  are  constructed  of  45-ft.  poles  with  8-in. 
tops  and  are  provided  with  two  cross-arms.  Attached  to  each  arm  are 
three  30,000-volt  dead-end  strain  insulators,  and  crossing  the  pond  be- 
tween the  insulators  on  the  upper  arms  are  strung  three  1/2-in.  stranded- 
steel  messenger  wires.  Suspended  from  the  messenger  wires  at  points 
dividing  the  span  into  three  parts  are  hangers  which  support  ordinary 
guy  strain  insulators.  Through  these  pass  the  main  copper  conductors, 
which  are  dead-ended  on  the  lower  set  of  insulators.  This  particular 
span  was  erected  in  July,  1913,  and  a  20-ft.  sag  was  allowed. 


Ill 

METERS 

Handling,  Identification,  Protection,  Rate  Checking,  Measurement  and 

Testing 

A  Labor-saving  Meter  Truck. — A  meter  truck  which  is  in  service  at 
the  laboratory  of  the  United  Electric  Light  Company,  of  Springfield, 
Mass.,  offers  a  good  home-made  means  for  facilitating  the  handling  of 
meters.  The  truck  is  5  ft.  6  in.  long  by  2  ft.  wide  and  is  built  with  double 
shelves,  its  carrying  capacity  when  loaded  being  forty-two  meters.  The 
frame  is  mounted  on  rubber-tired  wheels  and  is  equipped  with  substantial 
grab-handles  bolted  to  the  base  of  the  truck  with  iron  straps.  The  use  of 
rubber-tired  wheels  enables  the  truck  to  be  run  about  at  reasonable 
speed  without  endangering  the  moving  elements  of  the  meters  or  their 
suspensions. 

Tagging  Meter  Loops. — The  meter  department  of  a  Western  company 
which  keeps  ten  or  more  wiremen  busy  wiring  old  and  new  houses,  apart- 
ments, etc.,  employs  one  man  whose  sole  duty  is  to  check  and  tag  meter 
loops  after  the  wiring  is  in  place.  Aluminum  name  tags  are  used  for  this 
purpose,  the  company  having  purchased  outright,  for  $35,  a  stamping 
machine  similar  to  those  familiar  coin-operated  devices  installed  about 
railway  stations  and  other  public  places.  The  aluminum  strip  out  of 
which  the  plates  are  punched  costs  about  75  cents  per  pound,  making  the 
tags  inexpensive  as  well  as  durable.  The  tag  inspector  first  visits  the 
job  while  the  wiring  is  being  installed  and  traces  out  the  various  circuits, 
making  notes  of  the  labels  needed.  Returning  to  the  office,  he  stamps  out 
the  names  on  the  plates,  and  oh  the  next  day  he  affixes  the  tags. 

Protection  of  Electric  Meters  (By  Robert  Montgomery). — In  Fort 
Worth,  Tex.,  use  is  made  of  the  arrangement  shown  in  Fig.  1  to  protect 
meters  against  tampering,  while  still  permitting  the  customers  to  read 
them.  A  small  iron  terminal  box  is  fastened  to  the  meter  in  such  a 
way  that  it  cannot  be  removed  without  breaking  the  seals  of  the  meter, 
and  the  entrance  box  containing  the  switch  is  also  sealed.  This  method  is 
very  effective,  and  were  it  not  for  the  cost  and  the  difficulty  of  fastening 
the  terminal  box  to  the  meter  case  it  would  be  very  practicable.  The 
meter  manufacturers  can  furnish  a  solution  of  this  problem  with  very  lit- 
tle expense  by  providing  every  meter  with  a  device  for  fastening  it  to  a 
conduit  and  sealing  it.  In  1911  many  experiments  were  made  at  Fort 

56 


METERS 


57 


Worth  along  these  lines.  One  plan  is  indicated  in  Figs.  2,  3  and  4.  A 
meter  with  an  outlet  of  this  kind  could  be  installed  in  houses  already  wired 
in  conduit  as  is  shown  in  Fig.  5.  Where  a  residence  or  other  building 
was  wired  with  open  wiring  the  meter  could  be  arranged  as  shown  in 


ppedfor 
Conduit 


Bottom  View  of 
Buihlng  showing 
bow  the  Horse 
Shoe  Locks  the 
Bushing  In  Meter 


FIGS.    1,   2,   3  AND  4. DEVICES  USED  FOR  PROTECTING  METERS  AT 

FORT  WORTH,  TEXAS. 

Fig.  6.  In  places  where  it  is  not  necessary  to  protect  the  meter  it  could 
be  installed  as  shown  in  Fig.  7.  Fig.  4  shows  that  the  cast-iron  bush- 
ing can  first  be  screwed  on  the  conduit  and  the  meter  slipped  over  the 


~J  

If 

I 

13 
£ 

i 

1 

1 

1 

Hinged 


To  Service  Switch  or 
Center  of  Distribution 

Junction  Box  with  Fuse  and  Switch 

Cover  Sealed 

Meter 


Condulet  Out- 
let Screwed  in 
Bushing  when 
used  on  Open 
Wiring 


FIGS. 


6  AND  7. APPLICATION  OF  METER  PROTECTORS  TO  VARIOUS 

CLASSES  OF  WIRING. 


bushing.  Then  the  horseshoe  device  is  placed  over  the  bottom  of  the 
bushing,  thus  locking  the  meter  to  the  bushing  in  such  a  manner  that  it 
cannot  be  removed  unless  the  seals  of  the  meter  are  broken.  Another 


58  HANDBOOK  OF  ELECTRICAL  METHODS 

advantage  is  that  the  case  of  the  meter  would  not  be  strained  as  it  would 
be  if  the  conduit  is  screwed  directly  to  it. 

Two -meter  Off-peak  Rate  at  Salt  Lake  City. — To  any  customer  under 
its  retail  schedule  who  defrays  the  cost  of  a  time  switch  and  pays  the  mini- 
mum charge  for  a  second  meter  (making  a  total  minimum  of  $2  a  month), 
the  Utah  Light  &  Railway  Company,  of  Salt  Lake  City,  offers  off-peak 
energy  at  a  reduction  of  practically  one-half  its  full-rate  charge.  The 
peak  hours  during  which  the  two-meter  customer  is  charged  the  full  rate 
are  specified  for  each  month  in  the  year,  and  the  time-switch  settings  are 
changed  accordingly.  During  these  hours  the  time-switch  opens  the 
shunt  circuit  of  the  low-rate  meter  and  closes  that  of  the  high-rate  meter, 
transferring  the  registration  of  the  load  from  one  instrument  to  the  other. 


FIG.     1. TWO-METER  OFF-PEAK  RATE   CONNECTIONS,   SALT  LAKE  CITY. 

The  scheme  of  connections  is  shown  by  the  diagram,  Fig.  1.  The  cost 
of  the  time  switches  alone  on  those  installations  thus  far  put  in  service 
has  averaged  $25  per  switch,  the  best  grade  of  Anderson  and  Campbell 
clock  switches  being  used.  The  meter  department  of  the  Salt  Lake  Com- 
pany is  now  experimenting  with  the  construction  of  a  less  expensive 
switch  which  it  is  hoped  can  be  marketed  to  the  customer  for  $10  or  less, 
bringing  the  off-peak  schedule  more  within  the  grasp  of  the  average  user. 
An  inspector  mounted  on  a  motor  cycle  makes  weekly  rounds  of  the  two- 
meter  installations,  overlooking  them  and  setting  and  winding  the  clocks. 
The  customer,  however,  agrees,  if  requested,  to  keep  his  clock  mechanism 
wound. 

Use  of  Single -phase  Wattmeter  on  Polyphase  Circuit  (By  John 
Gilmartin). — In  measuring  the  load  on  three-phase  motors  in  industrial 
establishments  it  often  happens  that  high  accuracy  is  not  necessary  and 
a  single-phase  wattmeter  can  be  used,  the  load  being  assumed  to  be  bal- 
anced. The  most  usual  method  for  this  purpose  is  shown  in  Fig.  1, 
page  59,  where  the  series  coil  of  the  single-phase  wattmeter  is  inserted  in 
one  line  and  one  end  of  the  shunt  coil  is  connected  to  the  line  having  the 
series  coil  and  the  other  end  is  joined  successively  to  each  of  the  other  two 
lines.  The  algebraic  sum  of  the  two  successive  readings  is  the  three-phase 
load.  This  is  essentially  a  balanced  load  method,  as  it  assumes  that  the 
voltages,  currents  and  wattages  in  each  phase  are  equal. 


METERS 


59 


Fig.  2  shows  the  familiar  star-box  method  of  measuring  balanced 
three-phase  loads,  in  which  the  total  power  in  the  circuit  equals  the  watt- 
meter reading  multiplied  by  three.  The  two  external  resistances  con- 
nected to  the  lines  are  exactly  equal  to  each  other  and  to  the  resistance  of 
the  shunt  circuit  of  the  meter.  This  method  is  as  accurate  in  theory  as  that 
of  Fig.  1,  but  in  practice  would  usually  give  more  accurate  results,  because 
there  is  no  algebraic  summation  of  readings  to  be  made  and  no  chance  for 


FIG.    1. SINGLE-PHASE  WATTMETER  FOR  MEASURING  POLYPHASE  LOAD. 

error  due  to  the  load  changing,  as  may  happen  with  the  arrangement  of 
Fig.  1,  when  the  meter  is  dead  during  the  change  of  the  wattmeter  shunt- 
coil  tap  from  one  wire  to  the  other. 

The  objection  to  the  star-box  method  is  that  a  single-phase  indicating 
wattmeter  is  not  provided  with  a  star  box,  and  therefore  the  method  of  Fig. 
1  is  the  only  one  available  if  it  is  desired  to  measure  three-phase  power. 


FIG.    2. STAR-BOX  METHOD  OF  MEASURING  THREE-PHASE  LOAD. 

A  certain  company  has  adapted  its  single-phase  indicating  wattmeters 
for  use  in  a  star-box  arrangement,  as  illustrated  in  Fig.  3.  The  watt- 
meters in  question  were  self-contained  but  were  provided  with  external 
multipliers  for  extending  the  voltage  range  from  150  volts  to  300  and  600 
volts.  A  tap  was  brought  out  midway  between  the  2  tap  and  the  4  tap 
on  the  multiplier,  thus  giving  a  multiplier  of  three  and  making  the  resist- 
ance between  the  taps  equal  to  each  other  and  to  the  resistance  of  the 


60 


HANDBOOK  OF  ELECTRICAL  METHODS 


shunt  circuit  in  the  meter.  This  arrangement  provides  the  essentials 
for  the  star-box  method,  the  multiplier  being  connected  to  the  three-phase 
line,  as  shown  in  Fig.  3.  No  attention  need  be  paid  to  the  figures  given 
on  the  multiplier  to  apply  to  the  wattmeter  readings,  as  this  instrument 
now  reads  one-third  of  the  power  and  therefore  the  multiplying  factor  to 
be  used  is  three. 

This  discussion  applies  to  the  dynamometer-type  wattmeter,  and  the 
tap  on  the  multiplier  can  easily  be  located  by  simply  measuring  the  re- 
sistances with  a  Wheatstone  bridge. 


FIG.    3. SINGLE-PHASE  INDICATING  WATTMETER  USED  FOR  MEASURING  THREE- 
PHASE  LOAD. 

Ohmic  and  Inductive  Resistances  of  Meter-current  Circuits  (By 
H.  S.  Baker). — In  measuring  electrical  energy  by  a  watt-hour  meter 
certain  sources  of  error  are  commonly  neglected,  especially  where  the 
block  of  energy  being  measured  is  small.  The  errors  referred  to  are  those 
known  as  ratio  errors  and  phase  errors  of  series-instrument  transformers 
and  also  of  shunt-instrument  transformers  feeding  the  meter  circuit 
in  question.  The  ratio  and  phase  errors  of  a  series  transformer  are  de- 
pendent upon  the  ohmic  and  the  inductive  resistances  of  the  meter 
series  circuit  fed  and  upon  the  percentage  of  full-load  current  at 
which  the  series  transformer  is  operating.  Hence  the  accurate  cur- 
rent ratio  of  a  series  transformer  cannot  be  given  except  for  given 
conditions.  These  errors  frequently  exceed  1  per  cent,  of  the  rated 
full-load  amperage  of  the  transformer,  and  where  large  blocks  of 
energy  are  being  measured  the  correction  for  these  errors  will  soon 
more  than  pay  for  the  trouble  and  expense  of  such  determination 
and  correction.  An  outline  will  be  given  below  of  a  novel  method 
of  measuring  the  ohmic  and  inductive  resistances  of  a  given 
meter  circuit  (which  is  to  be  fed  by  the  series  transformer)  in  order  that 
the  operating  conditions  may  be  imposed  upon  the  transformer  while 


METERS 


61 


under  test.  The  following  method  of  measuring  the  above  circuit  con- 
stants requires  no  source  of  direct  current,  but  uses  the  polyphase  e.m.f. 
supply  which  feeds  the  meter.  Several  amperes  can  be  drawn  from  the 
secondary  of  a  shunt-instrument  transformer  for  a  minute  or  so  without 
running  any  risk  of  damaging  the  transformer.  The  method  consists, 
in  short,  of  measuring  upon  a  wattmeter  the  reaction  between  a  certain 
voltage  drop  A-B,  Fig.  1,  and  a  certain  current  fed  from  phases  2-3 
through  ohmic  resistance,  and  again  measuring  the  reaction  between  the 
same  voltage  drop  and  the  current  fed  from  phase  1-2.  The  case  described 
is  as  supplied  to  an  available  three-phase  e.m.f.  supply  1-2-3,  but  the 
method  is  easily  applicable  to  other  polyphase  circuits.  In  diagram  Fig. 
1  P,  Q,  R  and  S  are  nails  driven  in  a  board  and  connected  as  shown.  The 


FIQ.    1. DIAGRAM  OF  CONNECTIONS. 


rest  of  the  apparatus  shown  is  self-explanatory.  When  a  jumper  is 
placed  from  Q  to  R  it  will  be  seen  that  current  is  fed  through  the  series 
coil  of  the  wattmeter  and  through  the  meter  circuit  to  be  measured.  Now 
the  component  of  the  voltage  drop  A -B  which  is  in  step  with  the  current 
will  cause  the  wattmeter  to  deflect.  For  example,  if  the  reading  is,  say, 
28  watts  and  if  the  amperage  is,  say,  6,  then  the  ohmic  component  of 
the  drop  A-B  is  28 -=-6  =  4.66  volts  and  the  ohmic  resistance  from  A  to  B 
is  4. 66  -T-  6  =  0.78  ohm.  Now  remove  jumper  Q-R  and  place  jumpers  on 
P-Q  and  on  R-S,  thus  keeping  the  same  current  in  meter  circuit,  but 
changing  the  phase  of  the  current  in  the  wattmeter  series  coil.  The 
watt  reading  now  is,  say,  42.  In  diagram  Fig.  2  the  angle  3-2-1  is  60  deg., 
representing  the  two  phases  of  the  current  against  which  the  voltage 
drop  A-B  was  caused  to  react  in  the  wattmeter.  The  distance  2-X  is 


62  HANDBOOK  OF  ELECTRICAL  METHODS 

plotted  to  some  scale  to  twenty-eight  divisions,  and  the  distance  2-y  is 
plotted  equal  to  forty-two  divisions,  as  per  above  readings.  Perpendicu- 
lars are  erected  as  shown  at  X  and  y  and  their  intersection  at  P  is  the  end 
point  of  the  vector  2-P,  which  represents  the  voltage  drop  A-B,  and  2-X 
is  the  ohmic  component  and  X-P  is  the  inductive  component.  Scaling 
off  X-P  to  the  same  scale  it  is  found  to  be  32.3  divisions  or  "  inductive 
watts."  Then  the  inductive  volts  are  32.3-^6  =  5.38  volts  and  the 
inductive  resistance  is  5.38^6  =  0.9  ohm.  The  apparatus  required  for 
the  above  measurements  will  be  seen  to  be  simple  and  the  values  of  resist- 
ances obtained  are  reliable  within  a  few  per  cent.,  which  is  sufficiently 
accurate  for  the  purpose  in  hand,  as  the  total  effect  of  the  resistance  upon 
the  ratio  of  the  series-instrument  transformer  is  in  general  under  2 
per  cent. 

3, 


2 
FIG.    2. GRAPHIC  SOLUTION  OF  PROBLEM. 


Pendulum  Counting  Device  for  Testing  Meters. — For  testing  ro- 
tating-standard  meters  C.  B.  Stelle  of  the  Springfield  (Ohio)  Light,  Heat 
&  Power  Company,  makes  use  of  an  improved  pendulum  counting  device. 
Its  application  depends  upon  the  fact  that  if  T  be  taken  as  thirty-six 

seconds,  the  familiar  meter  expression  —  — ;=,—    -  becomes  merely  the 

product  of  the  constant  times  the  revolutions  multiplied  by  100,  a  result 
easily  computed.  The  device  shown  in  Fig.  1  comprises  a  one-second 
pendulum  and  counter  cam  which  automatically  connects  the  meter  in 
circuit  for  thirty-six-second  test  periods,  thus  fulfilling  the  above  condition. 
This  apparatus  avoids  the  use  of  a  stop  watch,  and  requires  only  one 
man  to  make  the  test.  It  also  tests  the  rotating  standard  from  start  to 
stop  each  time,  duplicating  the  conditions  of  the  test  meter's  practical 
use.  The  Springfield  company  emploj^s  two  rotating  standards,  one  of 
which  is  calibrated  every  three  days.  No  attempt  is  made  to  adjust  the 
standard,  but  a  calibration  curve  of  its  errors  at  varying  loads  is  prepared. 


METERS 


63 


The  39.5-in.  pendulum  shown  consists  of  a  wooden  rod  boiled  in  paraf- 
fine  and  carrying  solder-filled  bobs,  the  whole  being  hung  from  a  four- 
jewel  meter  bearing.  The  slight  impulse  needed  to  keep  the  pendulum  in 
continued  motion  is  supplied  by  the  solenoid  winding  at  the  left  of  the 
bob.  A  contact  pin  on  the  pendulum  swings  through  a  globule  of  mercury, 
actuating  the  counter  solenoid.  To  avoid  destructive  sparking  at  the 
contacts,  which  was  at  first  experienced,  these  contacts  simply  close 
secondary  windings  of  potential  transformers  whose  primaries  are  in  series 
with  the  solenoids  and  resistor  lamps.  As  long  as  the  secondaries  are 
open  the  current  passing  through  the  solenoid  is  small,  but  when  short- 
circuited  enough  current  flows  to  operate  the  mechanism. 


Jewel  Mounting 


Tra 


Soh  noid 


60-Cycle 
Supply 

FIG.    1. PENDULUM  COUNTING  DEVICE  FOR  TESTING  METERS. 

For  the  cam  wheel  a  couple  of  meter  disks  were  used,  one  having  been 
filed  with  sixty  teeth  and  the  other  having  its  periphery  cut  away  for  an 
arc  equal  to  thirty-six  of  the  teeth.  The  wheel  is  thus  rotated  through  the 
intervals  of  one  tooth  every  second,  completing  a  fullrotation  in  one  min- 
ute. For  thirty-six  seconds  of  this  period  the  contact  brush  bearing  on 
the  cam  surface  closes  the  meter  circuit,  breaking  it  again  automatically 
at  the  end  of  that  period.  By  means  of  the  double-throw  switch  at  the 
bottom  the  counting  device  may  be  disconnected  while  the  pendulum 
continues  in  operation.  This  feature  is  useful  while  warming  up  a  meter 
preparatory  to  making  the  test.  In  the  right-hand  position  both  pendu- 
lum and  counter  are  actuated.  The  mechanism  was  built  almost  entirely 
of  old  meter  and  arc-lamp  parts. 


64 


HANDBOOK  OF  ELECTRICAL  METHODS 


Testing  Shunt-type  Watt-hour  Meters  (By  R.  Toensf eldt) .— The  ac- 
curacy of  certain  meters  came  under  suspicion  when  it  was  found  that  the 
sum  of  the  panel  meter  readings  did  not  check  with  the  reading  of  the 
totalizing  meter.  In  order  to  find  which  was  inaccurate  it  was  decided  to 
calibrate  and  check  each  of  them.  The  meters  were  of  the  shunt  type 
operating  on  a  three-wire  system  and  having  one  coil  in  each  leg  of  the 
125/250- volt  lighting  circuit.  After  trying  several  methods  and  finding 
them  very  unsatisfactory,  it  was  decided  to  supply  the  watt-hour  meter 
directly  from  some  large  source  of  energy.  Accordingly  an  old  barrel  was 
rigged  up  as  a  water  rheostat  and  connected  in  series  with  a  set  of  terminals 
directly  across  the  125-volt  buses  on  the  board  as  shown  in  the  drawing, 
Fig.  1.  The  connecting  terminals  cc  are  two  independent  pieces  of  old  bus- 


125  V.  Buses 


FIG.    1. TESTING  SHUNT-TYPE  WATT-HOUR  METERS. 

bar,  tapped  and  provided  with  cap  screws,  which  were  made  merely  as  a 
convenience  for  connecting  the  meters  into  the  circuit.  The  coils  of  the 
watt-hour  meter  SiSz  were  connected  to  these  buses,  and  a  millivoltmeter 
v  connected  in  multiple  with  them.  An  ammeter  A  was  put  in  the  circuit 
chiefly  as  a  matter  of  check  on  the  current  taken  by  the  watt-hour  meter. 
By  varying  the  resistance  of  the  water  barrel  any  desired  drop  across  the 
terminals  of  the  watt-hour  meter  was  obtained.  Therefore,  considering 
80  millivolts  as  full-load  drop  across  the  meter  terminals,  this  figure  being 
obtained  from  the  manufacturers,  it  was  possible,  by  proper  manipulation 
of  the  rheostat,  to  apply  any  desired  load  to  the  watt-hour  meter.  The 
pressure  leads  of  the  meter  were  not  disturbed. 

The  test  was  made  in  the  usual  manner,  timing  a  certain  number  of 
revolutions  of  the  spindle,  calculating  from  this  the  number  of  kilowatt- 
hours  recorded  in  one  hour  and  comparing  this  with  the  load  calculated 
from  the  millivolt  drop. 


METERS  65 

In  testing  the  meters  for  a  perfectly  balanced  load,  the  testers  simply 
multiplied  the  meter  terminals  on  the  connectors;  that  is  to  say,  the  posi- 
tive terminal  from  the  positive  bus  and  the  positive  terminal  from 
the  negative  bus  on  the  same  connector  and  the  other  two  terminals  on 
the  other  connector.  In  this  way  each  coil  received  the  same  current, 
representing  a  perfectly  balanced  load.  For  unbalanced  conditions  one 
coil  was  left  open  and  the  other  was  tested  at  various  loads,  then  the  first 
tested  the  other  in  a  similar  manner  at  the  same  loads.  This,  of  course, 
would  represent  extreme  conditions,  but  it  was  believed  that  a  meter 
which  registers  correctly  under  these  severe  conditions  of  unbalancing  and 
also  on  condition  of  perfect  balance  will  be  reasonably  sure  of  giving  good 
results  on  intermediate  conditions. 

These  tests  proved  remarkably  convenient  and  efficient,  fulfilling  all 
expectations.  They  have  the  advantage  of  not  in  any  way  disturbing  the 
load  while  the  test  is  going  on,  only  affecting  the  load  records  for  the  time 
consumed  in  testing  and  adjusting,  which  can  easily  be  corrected  from  the 
previous  records.  No  large  currents  are  required  for  the  test  and  it  is 
not  necessary  to  unbalance  the  generators  more  than  25  per  cent,  to  obtain 
extremely  unbalanced  load  conditions. 

Ammeter  Testing  (By  G.  C.  Cassard). — There  are  two  generally 
recognized  methods  of  calibrating  direct-current  switchboard  ammeters 
under  operating  conditions.  In  the  first,  or  "  direct,"  method  a  stand- 
ard ammeter  (or  shunt  and  millivoltmeter)  is  connected  in  series  with  the 
shunt  of  the  meter  to  be  tested,  and  the  reading  of  the  latter  is  compared 
directly  with  that  of  the  standard.  In  the  second,  or  " potentiometer," 
method  the  drop  across  the  shunt  is  measured  by  using  a  potentiometer 
and  the  corresponding  current  is  taken  from  a  table  previously  compiled 
and  compared  with  the  reading  of  the  switchboard  meter. 

The  writer  has  no  intention  of  comparing  the  merits  of  these  two 
methods,  but  would  point  out  that  any  method  necessitating  connections 
directly  to  live  copper  and  depending  for  its  load  variation  on  manipula- 
tion of  the  outgoing  current  is  objectionable  and  should  not  be  tacitly 
accepted  without  an  effort  to  substitute  something  more  efficient. 

If  it  were  possible  to  measure  the  small  shunted  current  in  the  instru- 
ment itself,  for  instance,  and  to  know  what  scale  deflection  such  current 
would  produce,  it  would  be  quite  practicable  to  substitute  this  current  by 
using  a  small  battery  and  rheostat,  and  thus  to  make  the  test  in  a  position 
as  remote  from  the  switchboard  as  desired.  The  several  resistance  factors 
involved  would  have  to  be  known,  however,  to  accomplish  this  result, 
taking  account,  of  course,  of  the  actual  temperature  at  which  any  test 
might  be  made. 

As  an  imaginary  case,  suppose  that,  instead  of  using  a  shunt,  the 
ammeter  leads  have  been  simply  tapped  to  the  outgoing  copper  at  points 


66  HANDBOOK  OF  ELECTRICAL  METHODS 

3  ft.  or  4  ft.  apart  to  provide  the  necessary  drop.  This  introduces  a 
temperature  coefficient  in  this  part  of  the  circuit  and  is  assumed  simply  to 
present  a  case  involving  this  factor.  To  measure  the  resistance  of  this 
copper  section  it  will  be  necessary  to  disconnect  the  ammeter  leads  and 
measure  the  drop  between  these  points  with  a  potentiometer.  At  the 
same  time  the  current  is  measured  by  means  of  a  portable  ammeter  con- 
nected in  series.  Thus,  from  Ohm's  law,  the  resistance  of  this  copper  or 
" shunt"  at  the  observed  temperature  of  the  test  is  obtained.  Now  by 
applying  a  temperature  constant,  as  given  in  standard  tables,  this  resis- 
tance may  be  immediately  reduced  to  its  value  at  a  standard  temperature 
of  75  deg.  Fahr.  Thus,  calling  the  latter  resistance  R  and  X  the  resistance 
at  an  observed  temperature  of,  say,  66  deg.,  ^  =  1.02  X,  since  1.02  is 
the  constant  indicated  at  this  temperature.  This  value  R  is  then  stamped 
on  the  shunt,  and,  since  it  is  unchangeable,  it  constitutes  a  permanent 
record. 

To  measure  the  resistance  of  the  ammeter  leads  it  is  only  necessary  to 
attach  a  bridge  to  their  lower  ends  and  to  remove  the  upper  ends  from  the 
meter  and  bolt > them  together.  This  observed  resistance  is  then  reduced 
to  its  standard  resistance  at  75  deg.  just  as  was  done  with  the  shunt,  and 
this  standard,  r,  is  then  noted  on  a  tag  and  tied  to  the  leads. 

It  will  be  understood  that  the  above  work  is  preliminary  and  need  be 
performed  only  once,  so  long  as  absolutely  reliable  results  are  secured. 
The  values  obtained  are  obviously  unchangeable  and  may  be  used  in 
testing  for  an  unlimited  period.  There  remains  then  only  one  resistance 
to  be  measured — that  of  the  ammeter  itself — and  this  measurement  must 
necessarily  be  made  every  time  the  meter  is  checked;  indeed,  every  time 
the  tester  changes  the  internal  calibrating  coil,  which  is  usually  of  a  metal 
having  a  zero  temperature  coefficient  and  is  included  in  the  circuit  of  the 
copper  coils  of  the  instrument.  This  fact  has  no  bearing  on  the  results, 
however,  since  the  total  resistance  in  series  is  used  at  the  observed  tem- 
perature of  the  test,  and  is,  therefore,  not  to  be  affected  by  a  constant. 
R  and  r,  on  the  other  hand,  must  be  reduced  to  the  room  temperature 
before  being  used,  and  since  they  were  multiplied  by  a  factor  before  to 
bring  them  to  a  resistance  at  75  deg.  it  will  be  necessary  to  divide  them  by 
a  factor. 

By  reason  of  the  constant  relation  that  the  shunt  and  meter  bear  to 
each  other  at  all  loads,  and  by  the  simple  law  of  two  multiple  circuits, 

l~  :  ( -£  +  ri j  =  i  :  7,  in  which  R  is  the  shunt  resistance  at  75  deg.  Fahr. ; 

r  is  the  resistance  of  the  ammeter  leads  at  75  deg.  Fahr. ;  rx  is  the  observed 
resistance  of  the  ammeter;  K  is  the  temperature  factor  at  observed  tem- 
perature; i  is  the  current  in  the  meter  circuit,  and  /  is  the  current  in 
the  shunt. 


METERS 


67 


From  the  above  proportion  /  =  -•-  —  j~-  -  is  obtained  as  the  value  of 

*  iii 

the  current  in  the  shunt,  but,  as  the  current  through  the  meter  is  too  small 
to  be  read  on  its  own  scale,  this  value  may  be  taken  for  the  total  current 
external  to  the  shunt.  The  tester  may,  therefore,  take  the  meter  from 
the  board  and  after  connecting  up  to  a  suitable  bridge  and  milliammeter, 
and  measuring  the  resistance  and  current,  the  meter  may  be  calibrated  by 
above  formula. 

In  applying  a  system  of  testing  such  as  this  it  is  evident  that  recourse 
must  be  had  to  an  instrument  of  special  design,  which,  while  possessing 


FIG.    1. AMMETER  TESTING  SET. 


a  reasonable  degree  of  simplicity,  will  lend  itself  readily  to  the  measure- 
ment of  both  the  resistance  and  the  small  meter  current,  and  this  without 
undue  manipulation.  These  considerations  were  applied  in  designing  the 
testing  set  described  herewith,  which  may  be  made  up  in  a  form  compact 
enough  to  fit  into  a  small  suitcase.  (See  Fig.  1.) 

The  double-throw  switch  provides  for  the  uses  mentioned  by  changing 
the  arrangements  of  the  circuits.  The  measurement  of  resistance  is  made 
with  the  switch  thrown  to  the  right.  In  this  position  there  are  two  sub- 
circuits.  Starting  from  the  positive  side  of  the  battery  one  of  these 
circuits  passes  through  the  right  side  of  the  differential  galvanometer,  the 
resistance  dials,  the  upper  blade  of  the  switch  and  returns  to  the  battery. 
The  other  circuit,  starting  from  the  positive  side,  passes  through  the  lower 


68  HANDBOOK  OF  ELECTRICAL  METHODS 

blade  of  the  switch,  the  left  side  of  the  galvanometer,  the  terminals  CD 
(supposing  the  terminals  to  be  bolted  together)  and  back  to  the  battery. 
The  two  circuits  from  the  junction  A  to  the  junction  B  are  of  equal 
resistance  when  the  three  resistance  dials  are  set  at  zero;  therefore,  any 
outside  resistance  connected  between  C  and  D  may  be  accurately  meas- 
ured to  thousandths  of  an  ohm  by  balancing  the  galvanometer  by  the 
dials.  By  attaching  these  terminals  to  the  binding  posts  of  the  meter  its 
internal  resistance  is  first  measured.  Since  this  same  connection  is  used 
for  the  current  measurement  the  tester  may  proceed  by  simply  throwing 
the  switch  to  the  left.  Now  there  is  only  one  circuit,  starting  at  positive, 
right  side  of  galvanometer,  resistance  dials,  milliammeter,  lower  blade  of 
switch,  left  side  of  galvanometer,  ammeter  on  test  and  back  to  the  battery. 
In  this  position  the  galvanometer  is  not  in  use,  but  the  milliammeter  is, 
and  it  is  found  desirable  to  pass  the  current  through  the  galvanometer 
twice  for  three  reasons:  First,  since  the  current  is  the  same  in  the  two 
coils  it  will  not  deflect  the  needle;  second,  the  increased  resistance  of  the 
series  connection  added  to  that  of  the  milliammeter  which  has  just  been 
switched  in  reduces  the  current  flow  when  calibrating,  so  that  greater 
battery  strength  may  be  used  to  give  the  galvanometer  greater  sensitive- 
ness when  balancing,  and,  third,  with  the  series  connection  the  galvano- 
meter itself  may  be  checked  as  to  whether  or  not  it  is  perfectly  differential. 

In  the  calibrating  position  of  the  switch  it  makes  no  difference  in  the 
accuracy  of  the  ammeter  how  much  resistance  is  in  circuit,  provided  the 
resistance  of  the  calibrating  coil  inside  the  ammeter  is  not  changed.  This 
seems  inconsistent  until  it  is  remembered  that  a  change  in  the  calibrating 
coil  means  a  change  in  the  ratio  of  the  meter  to  its  shunt — that  is,  a  change 
in  the  value  of  one  factor  (ri)  of  the  formula,  which  change  should  only 
be  made  in  changing  the  calibration.  So  for  varying  the  load  the  dial 
resistances  are  varied,  but  not  read,  the  actual  checking  being  made  by 
the  reading  of  the  milliammeter  as  compared  with  the  ammeter. 

Testing  Large  Watt-hour  Meters  on  Fluctuating  Loads  (By  F.  A.  Laws 
and  C.  H.  Ingalls). — All  persons  responsible  for  the  upkeep  of  large  di- 
rect-current wattmeters  which  are  used  on  a  rapidly  fluctuating  load, 
have  experienced  difficulties  in  the  testing  and  adjustment  of  such  meters. 
Owing  to  the  large  number  of  readings  of  the  current  which  it  is  necessary 
to  take  in  order  to  obtain  a  good  average  the  ordinary  method  of  using 
a  stop-watch  and  of  measuring  the  line  voltage  and  current  is  a  time- 
consuming  operation,  and  in  some  cases  the  fluctuations  are  so  rapid  that 
the  use  of  the  ammeter  is  quite  out  of  the  question.  An  alternative 
procedure  is  to  take  the  meter  out  of  service  and  to  send  through  its  coils 
the  current  from  a  storage  battery.  This  current  may  be  controlled  by 
resistors,  so  that  tests  at  light  load  and  up  to  400  amp.  may  be  made  with- 
out the  apparatus  being  too  unwieldy  to  be  managed  by  two  persons.  For 


METERS 


69 


the  purpose  a  couple  of  Edison  cells  are  convenient,  being  readily  portable. 
It  is,  however,  desirable  to  avoid  taking  the  meter  out  of  service,  and  to 
make  the  test  with  the  customer's  regular  load.  These  considerations  have 
led  us  to  devise  other  methods  of  attacking  the  problem. 

The  very  convenient  forms  of  test  meters  developed  for  alternating- 
current  work  naturally  suggested  similar  devices  for  use  on  direct-current 
circuits.  Such  test  meters  are  made  up  to  a  capacity  of  150  amp.  But 
for  our  purposes  we  desire  meters  which  will  take  currents  from  500  amp. 
up  to  the  largest  magnitudes  met  with  in  practice.  The  direct  application 
of  shunts  to  a  test  meter  of  the  ordinary  commutator  form  is  not  admissible. 
Since  we  desired  to  retain  this  type  of  meter,  the  following  methods  of 


FIG.    1. DIFFERENTIAL  MULTIPLIER  ARRANGEMENT. 

dealing  with  the  problem  were  devised;  they  may  be  regarded  as  arrange- 
ments by  which  shunts  may  be  so  applied  to  the  test  meter  that  errors 
due  to  contact  resistances  and  heating  are  obviated. 

The  first  method  is  shown  in  Fig.  1,  where  for  the  sake  of  simplicity 
the  potential  connections  to  the  meters  are  omitted.  The  arrangement 
may  be  called  a  differential  multiplier,  for  by  it  the  range  of  the  test  meter 
is  extended,  in  this  case  approximately  thirty-fold. 

The  station  busbar  is  arranged  so  that  it  has  a  narrow  gap  at  G.  This 
gap  is  ordinarily  closed  by  plates  firmly  bolted  in  position.  The  gap  should 
be  narrow  and  the  leads  so  arranged  that  the  field  at  the  meter  is  not  dis- 
arranged when  the  gap  is  opened.  The  entire  current  flows  to  a,  where 
it  divides,  a  comparatively  small  portion  flowing  through  the  fine  wire 
coils  of  the  multiplier  MM',  the  test  meter  and  the  adjustable  resistor  r 
to  6.  The  main  portion  flows  through  the  " coarse  coil"  C  of  the  multi- 
plier, which  is  in  this  case  a  straight  bar,  then  through  the  resistor  R, 


70 


HANDBOOK  OF  ELECTRICAL  METHODS 


which  is  of  such  a  magnitude  as  to  give  the  voltage  drop  required  in  the 
test-meter  circuit.  The  fields  due  to  the  currents  in  MM'  and  C  are  op- 
posed, and  in  them  is  placed  an  astatic  movable  coil  system  which  is  pro- 
vided with  pivots  and  a  damping  device.  The  movable  member,  in 
series  with  a  suitable  resistor,  is  placed  across  the  line  and  serves  to  show 
when  the  fields  due  to  C  and  MM'  are  balanced.  In  the  present  instru- 
ment 30.7  amp.  in  C  is  required  to  balance  1  amp.  in  MM'.  The  multi- 
plier is  brought  to  a  balance  by  varying  r.  When  this  has  been  done  the 
corrected  watt-hours  by  the  test  meter  are  obtained  by  multiplying  its 
indications  by  31.7. 

The  test  meter  is  of  course  set  up  where  it  will  be  as  free  from  stray 
field  effects  as  possible.  The  leads  to  it  are  flexible  and  readings  are 
taken  with  the  meter  in  four  different  azimuths  90  deg.  apart.  For  our 
work  this  has  sufficed;  but  conditions  may  be  easily  imagined  where, 
owing  to  the  change  in  the  distribution  of  current  between  feeders  which 


Diff.  M.V. 
FIG.    2. ARRANGEMENT  ACCORDING  TO  TWO-RESISTOR  METHOD. 

are  at  different  distances  from  the  test  meter,  this  procedure  would  not 
give  the  desired  result.  In  such  cases  a  shielded  instrument  would  be 
desirable.  The  multiplier  being  astatic,  with  the  centers  of  the  upper 
and  lower  coils  2  1/2  in.  apart,  it  is  not  affected  by  uniform  stray  fields. 
Anything  that  produces  a  non-uniform  stray  field — for  instance  a  busbar 
close  to  the  instrument — might,  however,  lead  to  a  mis  judgment  of  the 
balance.  So  the  apparatus  should  be  set  up  at  a  fair  distance  from  the 
switchboard. 

Appreciation  of  this  possible  difficulty  led  to  the  second  method, 
which  employs  two  appropriate  resistors,  one  in  the  circuit  of  the  test 
meter  and  the  other  in  the  parallel  circuit,  the  potential  drops  in  the  two 
being  made  equal  by  the  adjustable  resistor  r  and  this  equality  indicated 
by  a  differential  millivoltmeter  of  the  D'Arsonval  pattern.  This  arrange- 
ment is  indicated  in  Fig.  2.  Any  shunts  which  are  suited  to  the  purpose 


METERS 


71 


may  be  temporarily  bolted  together  and  used  for  Si  and  S2.  They 
should,  of  course,  be  free  from  thermal  e.m.f.  errors.  We  have  found 
this  matter  troublesome  in  some  cases. 

This  arrangement  may  be  simplified  and  the  differential  millivolt- 
meter  replaced  by  a  pivoted  D'Arsonval  galvanometer  if  a  special  shunt 


FIG.    3. SIMPLIFIED  TWO-RESISTOR  METHOD. 

be  constructed  for  the  purpose.     The  last  plan  is  indicated  in  Fig.  3. 

The  sections  of  the  shunt  (see  Fig.  4)  Si  and  82  have  a  common  terminal 

T       Sf 
at  a.     If  the  galvanometer  stands  at  zero  then  -,-  =  -a-  and  the  corrected 

*2        01 


FIG.    4. SHUNTS  USED  IN  SIMPLIFIED  METHOD. 

reading  of  the  test  meter  is  its  indication  multiplied  by  —l-j — -.     By  the 

*2 

use  of  two  potentiometers  to  measure  /i  and  72  when  the  galvanometer  is 
balanced  this  factor  can  be  very  accurately  determined  once  for  all. 

6 


72  HANDBOOK  OF  ELECTRICAL  METHODS 

This  is  the  final  form  of  the  apparatus  and  one  which  has  been  used  very 
successfully  for  over  a  year. 

The  capacity  of  the  test  meter  is  40  amp.  Two  sets  of  shunts  and 
auxiliary  resistances  R  are  mounted  on  the  same  base;  the  ratings  are 
1000  amp.  and  2000  amp.  The  voltage  drop  in  the  shunts  at  full  load 
is  100  millivolts  and  in  the  resistor  R  it  is  400  millivolts.  The  adjustable 
resistor  r  is  a  strip  of  Baker  metal,  the  effective  length  of  which  can  be 
altered  by  the  use  of  screw  clamps.  Placed  in  parallel  with  the  strip  is 
a  carbon  compression  rheostat  by  which  the  fine  adjustment  is  affected. 

The  entire  apparatus,  including  the  necessary  cables  but  not  the  test 
meter,  may  be  stowed  away  in  a  chest  31  1/2  in.  by  19  in.  by  14  in.  which 
can  be  conveniently  shipped  from  station  to  station. 

A  Portable  Stand  for  Graphic  Instruments  (By  H.  H.  Kenney).— 
Graphic,  or  curve-drawing,  electrical  meters  are  very  useful  to  concerns 
that  employ  many  motors  because  with  a  graphic  instrument  a  permanent 
accurate  record  of  motor  performance  can  be  obtained.  The  curve, 
usually  reading  in  either  amperes  or  watts,  indicates  clearly  what  the 
average,  maximum  and  minimum  inputs  to  the  motor  are  and  it  shows 
the  time  relations  between  them.  It  is  impracticable  to  obtain  significant 
records  of  these  characteristics  through  the  use  of  indicating  instruments. 
In  a  reasonably  large  concern  a  graphic  instrument  will  usually  pay  for 
itself  the  first  year  it  is  used  by  enabling  its  purchaser  to  select  motors  of 
the  smallest  capacity  that  will  do  the  work. 

When  a  motor  drive  for  a  new  machine  or  application  having  unknown 
input  characteristics  is  being  arranged  a  spare  motor  should  be  geared 
to  it  temporarily.  The  input  to  the  motor  should  be  measured  and 
recorded  with  a  graphic  instrument.  From  the  curve  thus  obtained  it 
will  be  possible  to  determine  to  a  certainty  the  size  of  motor  that  should  be 
purchased.  No  margin  need  be  allowed  so  that  the  motor  may  be  quite 
big  enough.  If  necessary  a  curve-drawing  instrument  can  be  inserted 
in  the  motor  circuit  and  be  left  there  for  a  day  or  a  week  or  a  month,  and 
it  will,  with  little  attention,  accurately  record  what  the  input  requirements 
to  the  motor  have  been  for  each  interval  of  the  time  during  the  period. 

Obviously,  for  such  functions  a  graphic  meter  must  be  portable.  It 
must  be  so  arranged  that  it  can  be  easily  transported  to  and  set  up  at  any 
point  in  the  plant.  The  better  types  of  curve-drawing  instruments  have 
been  designed  for  switchboard  mounting,  so  that  if  they  are  to  be  made 
portable  a  special  stand  must  be  arranged  for  them.  Fig.  1  shows  a  type 
of  stand  that  is  easy  to  make  and  cheap,  and  which  will  give  good  service. 

Referring  to  Fig.  1:  The  stand  is  composed  of  three  pieces  of  board 
about  11/2  in.  thick.  The  actual  thickness  of  the  back  board  is  deter- 
mined by  the  thickness  of  the  switchboard  panel  for  which  the  studs  and 
supporting  bolts  on  the  instrument  are  designed.  Thoroughly  dried 


METERS 


73 


wood  should  be  chosen  for  the  support  and  a  wood  that  will  not  warp 
readily  is  much  to  be  preferred.  The  component  pieces  are  held  together 
with  screws  and  they  can  be  mortised  one  into  the  other  if  desired.  After 
assembling,  the  whole  should  be  well  varnished  to  prevent  any  possibility 
of  warping.  The  sizes  of  the  component  pieces  of  board  and  the  locations 

Curve  Drawing  Meter 


Leveling 
Screw 


Brace 


Side  Elevation  Rear  Elevation 

FIG.    1. STAND  FOR  GRAPHIC  METER. 


Bore  Hole  Vic  Larger  in 

^       L. i  Diameter  than 

Diameter  of  Bolt 


Nut  Set  in  Depression 
Section  A  A 


FIG.    2. — DETAIL  OF  LEVELING 
SCREW. 


Bottom  View 

FIG.    3. — ARRANGEMENT  FOR 
LEVELING  SCREW  NUT. 


of  the  stud  and  bolt  holes  depend  on  the  make  of  meter  that  is  to  be 
mounted.  The  manufacturer  of  the  instrument  will  furnish  a  drilling 
templet  and  an  outline  drawing  of  it,  but  it  is  probably  better  to  take 
dimensions  from  the  instrument  after  it  has  been  received. 

Four  leveling  screws,  one  in  each  corner,  are  arranged  in  the  bottom 
board.     A  meter  of  this  type  must  be  quite  accurately  leveled  if  a  true 


74  HANDBOOK  OF  ELECTRICAL  METHODS 

record  is  expected.  The  leveling  screws  are  constructed  as  delineated  in 
Figs.  2  and  3.  The  screw  itself,  Fig.  2,  is  made  by  inserting  a  slightly 
tapered  pin  through  a  hole  drilled  through  the  head  of  a  hexagonal  head 
tap-bolt  of  about  3/8-in.  diameter.  The  pin,  which  serves  as  a  handle, 
is  formed  from  a  drill  or  brass  rod.  It  is  driven  snugly  into  the  hole  and 
because  of  its  taper,  will  stay  there.  The  nuts  through  which  the  leveling 
screws  turn  are  arranged  as  detailed  in  Fig.  3.  A  square  iron  nut  is 
tightly  fitted  into  a  depression  cut  in  the  bottom  of  the  bottom  board 
and  a  metal  plate,  fastened  over  it  with  wood  screws,  retains  it.  The 
round  hole  through  the  board  for  the  leveling  screw  should  be  bored  some- 
what larger  than  the  diameter  of  the  screw  so  that  there  will  be  ample 
clearance. 

Directions  for  the  arrangement  of  electrical  connections  cannot  be 
given  because  they  are  different  for  each  make  of  instrument.  For  direct- 
current  installations,  where  the  voltage  regulation  is  reasonably  good,  a 
graphic  ammeter  will  draw  curves*  which,  by  taking  into  account  the 
voltage  (which  is  assumed  to  be  constant)  can  be  calibrated  in  watts  or 
horse-power.  An  ammeter  is  simpler  than  a  wattmeter,  is  more  easily 
connected  and  is,  on  the  whole,  preferable  for  direct-current  work.  But 
in  alternating-current  work,  where  low  power  factors  are  encountered  and 
where  the  current  taken  by  a  motor  may  not  be  at  all  proportional  to  the 
actual  power  consumed,  a  wattmeter  must  be  used. 

One  graphic  instrument  can  be  made  to  record  the  inputs  to  motors 
of  small,  large  or  intermediate  capacities  and  of  different  voltages  by 
providing  suitable  shunts  and  multipliers  for  direct-current  instruments 
and  series  and  shunt  transformers  for  alternating-current  instruments. 
The  electrical  manufacturers  do  not  regularly  list  these  "wide  range" 
outfits,  but  on  application  will  furnish  data  concerning  them. 

Watt-hour  Meter  Testing  for  Central  Stations  (By  C.  W.  Ward  and 
H.  N.  Stroh). — The  writers  have  designed  and  put  in  use  for  the  Duquesne 
Light  Company,  Pittsburgh,  a  test  board  or  rack  in  which  two  or  more 
portable  service  types  of  rotating  standard  watt-hour  meters  may  be 
checked  at  the  same  time  against  a  carefully  calibrated  laboratory  rotating 
standard.  The  device  reduces  to  a  minimum  the  labor  expense  involved 
in  the  weekly  checking  of  a  number  of  portable  standards,  yet  enables 
the  inspector  to  maintain  a  very  high  degree  of  accuracy. 

Primarily  the  rack  is  a  large  container  built  to  accommodate  the  num- 
ber of  rotating  standards  desired.  Westinghouse  standards  of  the  5-amp. 
to  40-amp.,  100-200-volt  type  are  employed  by  the  Duquesne  Light  Com- 
pany, and  the  rack  in  use  is  built  for  twenty  standards.  The  rack  can, 
of  course,  be  built  to  accommodate  any  type  of  standard. 

From  the  accompanying  Figs.  1  and  2  one  can  see  at  a  glance  the 
adaptability  of  the  rack  and  realize  what  a  time  saver  it  is. 


METERS 


75 


The  meter  movements  as  a  whole  are  removed  from  their  wood- 
carrying  cases  and  their  drums  and  contact  fingers  are  carefully  inspected, 
after  which  dust  and  foreign  particles  are  blown  out  with  heated  compressed 
air.  The  complete  movements  are  then  inserted  in  the  various  compart- 
ments as  shown.  These  compartments  are  so  designed  that  the  ele- 
ment has  as  exact  a  fit  as  when  in  its  carrying  case,  being  level,  sealed  from 


FIG.     1. FRONT  VIEW  OF  RACK. 


FIG.    2. REAR  VIEW  OF  RACK,  SHOWING   CURRENT  BASES  AND  POTENTIAL 

CIRCUITS. 

air  currents,  and  with  the  shunt  (potential)  coils  automatically  cut  into 
the  circuit  on  the  under  side  of  the  potential  binding  posts  through  the 
medium  of  the  two  springs  shown  on  the  left  side  of  each  compartment. 
These  springs  make  a  most  positive  connection  and  cannot  get  out  of 
order. 


76  HANDBOOK  OF  ELECTRICAL  METHODS 

The  potential-coil  connections  are  wired  up  in  a  special  way  to  com- 
pensate for  the  drop  in  voltage  when  a  large  number  of  the  standards  are 
being  checked  at  one  time. 

The  series  (current)  connections  to  the  standards  are  made  by  short, 
flexible  leads  coming  up  from  the  rear  of  the  rack,  along  which  run  two 
flat  copper  buses,  each  capable  of  carrying  100  amp.  From  the  sketch 
showing  the  rear  of  the  rack  it  will  be  seen  that  these  strips  are  split  al- 
ternately at  each  meter  and  that  no  two  adjacent  meters  are  cut  in  on  the 
same  strip  or  bus.  Such  an  arrangement  neutralizes  the  effects  of  any 
stray  fields  set  up  by  these  buses..  The  master  meter  employed  as 
standard  is  of  the  regular  Westinghouse  rotating  type  with  a  few 
special  modifications  insuring  greater  accuracy  and  facility  of  handling. 

Testing  includes  a  check  upon  each  series  and  shunt  instrument  wind- 
ing and  the  error  taken  as  final  in  each  test  is  the  average  of  three  checks 
under  each  condition. 

The  usual  method  of  returning  to  zero  the  pointer  of  each  meter  being 
checked  is  to  employ  a  switch  in  the  potential  circuit  of  each.  This  method 
is  slow  and  unsatisfactory.  On  this  rack  the  front  is  hinged  so  that  it 
drops  down  with  counter-weights,  thus  exposing  the  moving  element  of 
each  standard.  The  disk  is  then  turned  by  a  light  pressure  of  the  finger 
and  the  pointer  brought  exactly  to  zero  at  once.  The  calibration  card  foi 
each  meter  is  always  exposed  for  entries,  being  held  by  a  spring  clip  on  a 
small  shelf  directly  in  front  of  its  respective  meter.  This  shelf  also  pre- 
vents the  warping  of  the  hinged  door,  which  effectively  seals  each  com- 
partment against  the  influence  of  air  currents.  A  latch  similar  to  that 
employed  on  refrigerators  is  used  to  hold  this  swinging  front  tightly  in 
place  when  closed.  Shelves  are  made  underneath  each  compartment 
for  the  storing  of  the  empty  meter  cases  while  the  elements  are  under  test. 
A  hinged  cover  fits  over  the  entire  top  of  the  rack,  which  is  closed  when 
not  in  use. 

Each  series  winding  is  tested  at  full,  half,  tenth  and  twentieth  load 
current  and  at  both  voltages,  a  total  of  ninety-six  tests  for  each  meter. 
These  tests  are  made  on  Sunday,  all  standards  being  brought  in  Saturday 
by  the  testers.  Thus  on  Monday  morning  a  carefully  calibrated  standard 
is  ready  for  each  tester  for  his  week's  work. 


IV 
OPERATION  OF,  'AND  CHANGES  IN  CIRCUITS 

Operation  of  Various  Kinds  of  Circuits,  Reducing  Voltage  Fluctuations 
by  Different  Means  and  Checking  of  Voltage  Variations 

Operation  of  a  Two-phase  Distribution  System  (By  Alden  W. 
Welch). — Where  energy  is  transmitted  over  a  three-phase,  25-cycle; 
6600-volt  circuit  two-phase  current  is  usually  obtained  by  use  of  a  fre- 
quency changer  consisting  of  a  three-phase,  25-cycle,  6600-volt  motor, 
direct-connected  to  a  two-phase,  60-cycle,  2700-volt  generator.  The 
two  windings  of  the  generator  sometimes  have  a  common  connection,  but 
more  often  the  two  phases  are  entirely  independent  of  each  other.  At  one 
time  it  was  the  practice  to  connect  the  two  phases  in  series  and  run  a 
common  wire  from  their  intersection,  since  by  this  method  three  wires 
were  sufficient,  while  four  were  required  for  the  operation  of  the  two  phases 
independently.  The  great  disadvantage  of  this  scheme  is  that  if  trouble 
occurs  on  one  phase  it  will  affect  the  operation  of  the  other.  A  ground 
on  one  of  the  outside  legs  will  produce  a  strain  between  the  other  outside 
leg  and  the  ground  equal  to  1.41  times  the  volts  per  phase.  The  practice 
now  is  to  transmit  with  four  wires  from  independent  phases  and  distribute 
with  three  wires  from  either  one  single-phase  transformer  having  a  split 
winding,  if  single  phase  is  desired,  or  from  two  single-phase  transformers 
having  their  windings  connected  for  two-phase  service. 

When  a  number  of  customers  in  the  same  vicinity  using  both  lamps  and 
motors  are  to  be  served  with  energy,  it  is  customary  to  make  use  of  a  four- 
wire,  two-phase  secondary.  In  this  case  the  secondary  of  the  transformer 
on  one  phase  is  connected  to  a  three- wire,  120-volt  service  which  feeds  the 
lamp  circuits,  while  for  the  motor  circuits  a  second  transformer,  connected 
for  two-wire,  240  volts  is  used.  One  secondary  terminal  of  this  trans- 
former is  connected  to  one  outside  secondary  terminal  of  the  lighting 
transformer  and  the  other  terminal  forms  the  fourth  wire  of  the  second- 
ary circuit.  The  wire  running  from  the  junction  of  the  two  transformers 
forms  the  common  wire  for  the  two-phase  motors,  the  first  and  fourth  wire 
being  connected  to  the  phase  terminals  of  the  motors.  Reference  to  the 
diagram,  Fig.  1,  will  make  clear  this  method  of  operation.  This 
method  should  not  be  used  where  the  motor  and  lighting  loads  are  simul- 
taneous. The  usual  condition  met  with  is  that  the  motors  are  operated 

77 


78 


HANDBOOK  OF  ELECTRICAL  METHODS 


during  the  day,  while  the  lamps  burn  only  at  night.  This  maintains  a 
balanced  condition  on  the  secondary. 

The  voltage  is  controlled  by  either  a  hand-operated  or  an  automatic 
regulator.  The  latter  method  has  been  tried  with  great  success,  and  fol- 
lowing is  a  brief  description  of  such  a  regulator.  The  control  part  of  this 
apparatus  is  a  contact-making  voltmeter  which  consists  of  a  solenoid  hav- 
ing a  shunt  winding  and  a  series  winding  acting  in  opposition.  Mounted 
on  a  support  is  a  lever,  on  one  end  of  which  are  two  contact  points  and 
on  the  other  end  is  a  core  which  is  free  to  move  within  the  solenoid.  The 
contact  points  on  the  movable  lever  control  the  energy  used  in  the  relay 
switch,  which  in  turn  controls  the  circuit  for  operating  the  motor  of  the 
regulator. 

In  series  with  the  shunt  winding  is  a  non-inductive  resistance  having 
taps  for  various  voltages.  The  resistance  is  of  such  value  that  a  current  of 


WVW 

ywwwv 


FIG.     1. OPERATION   OF  A  TWO-PHASE  DISTRIBUTION  SYSTEM. 

about  0.8  amp.  is  carried  in  the  shunt  winding.  The  potential  tap  used 
for  two-phase  feeders  is  usually  120  volts.  The  series  windings  are 
divided  into  seven  fine  and  two  coarse  adjustment  windings,  each  of  the 
coarse  windings  having  about  seven  times  the  effect  of  a  fine  one. 

In  calibrating  the  contact-making  voltmeter  a  spring  on  the  lever  is 
adjusted  until  the  lever  balances  between  the  contacts  with  120  volts 
on  the  shunt  winding  and  no  current  in  the  series  coils.  In  order  that  the 
contact-making  voltmeter  may  compensate  for  the  IR  drop  on  the  feeder 
at  all  loads,  the  number  of  series  turns  is  adjusted  to  maintain  normal 
voltage  at  a  time  when  the  feeder  is  carrying  a  heavy  load  at  a  power- 
factor  of  90  per  cent,  until  the  effect  of  the  ampere-turns  due  to  the  cur- 
rent is  equal  and  opposite  to  that  produced  by  the  shunt  coils,  the  lever 
balancing  between  the  relay  contacts. 

Any  increase  in  load  on  the  feeder  naturally  increases  the  ampere- 
turns  in  the  series  coil  and  causes  it  to  draw  the  core  downward,  the  lever 
making  contact  on  the  upper  stud.  This  operates  the  relay  switch, 
causing  the  motor  to  operate  the  regulator  in  a  direction  to  increase  the 


OPERATION  OF  AND  CHANGES  IN  CIRCUITS  79 

voltage  until  the  pull  exerted  by  the  shunt  coil  balances  that  in  the  series 
coil.  As  the  load  decreases  on  the  feeders  the  pull  in  the  series  coil 
decreases  and  the  core  is  drawn  upward,  causing  contact  to  be  made  on 
the  lower  stud.  This  energizes  the  relay  in  the  lowering  position  and  the 
regulator  continues  to  lower  the  voltage  until  a  balance  is  again  restored  to 
the  solenoid  windings. 

For  regulating  the  voltage  of  highly  inductive  circuits  use  is  made  of  a 
compensating  voltmeter.  This  instrument  compensates  for  the  induc- 
tance and  IR  drop,  and  is  used  for  maintaining  a  predetermined  voltage  at 
the  point  of  distribution  irrespective  of  load  or  power-factor.  The  regu- 
lator should  be  connected  between  the  feeder  switch  and  the  series 
transformer  so  that  the  ammeter  will  indicate  the  exact  load  carried  by  the 
feeder  and  not  include  that  taken  by  the  regulator.  This  is  essential  to 
good  voltage  regulation. 

The  following  is  the  method  for  determining  at  what  pressure  a  two- 
phase  feeder  should  be  operated  when  hand-operated  or  motor-operated 
regulators  are  used.  The  feeder  is  covered  by  testers.  One  is  usually 
sufficient,  but  for  feeders  extending  over  a  large  area  two  or  more  testers 
are  necessary  in  order  to  obtain  satisfactory  results.  Pressure  readings 
are  taken  by  means  of  an  alternating-current  voltmeter  at  the  cut-outs  of 
certain  customers,  the  aim  being  to  obtain  a  general  idea  of  the  pressure 
conditions  in  all  parts  of  the  feeder.  If  the  voltage  is  found  to  be  nearly 
normal  over  the  whole  feeder,  especially  in  the  districts  of  heaviest  load, 
a  certain  customer  is  selected  on  each  phase,  usually  in  the  section  of  the 
heaviest  load.  These  two  locations  are  termed  the  balancing  points  and 
it  is  assumed  that,  conditions  remaining  the  same,  when  the  pressure  is 
normal  at  these  points  the  entire  feeder  is  operating  at  satisfactory 
pressure. 

At  the  balancing  points,  the  station  from  which  the  feeder  is  being 
operated  is  called  up  by  telephone  and  readings  are  obtained  of  the  feeder 
load  and  feeder  pressure  as  indicated  by  the  station  instruments.  From 
the  data  obtained  a  curve  is  plotted,  having  feeder  loads  in  amperes  as 
abscissas  and  feeder  pressures  as  ordinates.  If  120  volts  is  considered 
normal  pressure  at  the  balancing  points,  and  when  that  voltage  is  read 
the  feeder  is  carrying  50  amp.  high  tension,  at  130  volts  feeder  pressure 
at  the  station,  read  through  shunt  transformers,  the  curve  would  start  at 
0  amp.  and  120  volts  and  pass  through  the  point  on  the  sheet  represent- 
ing 50  amp.  at  130  volts.  Two  similar  curves,  one  for  each  phase,  are 
drawn  on  the  same  sheet. 

If  the  loads  on  the  two  phases  are  nearly  equal  and  correspondingly 
distributed,  the  two  points  representing  the  respective  loads  on  the  two 
phases  should  be  plotted  and  a  curve  drawn  bisecting  the  space  between 
these  points.  The  curve  so  determined  should  be  used  for  operating 


80 


HANDBOOK  OF  ELECTRICAL  METHODS 


both  phases.  If  the  loads  on  the  two  phases  are  not  evenly  distributed; 
curves  of  both  phases  should  be  plotted  on  the  same  sheet.  Under  these 
conditions  the  two  phases  of  the  feeder  would  be  regulated  by  different 
curves. 

Curve  A,  Fig.  2,  represents  the  previously  noted  condition  when  the 
conditions  affecting  the  operation  of  the  two  phases  are  equal.  Operating 
curves  B  and  C  do  not  coincide  with  each  other,  but  the  difference  between 
them  is  so  slight  that  curve  D  may  be  drawn  bisecting  the  space  between 
them.  D  now  becomes  the  operating  curve  for  the  feeder,  B  and  C  being 


150 


1-10 


a  130 


120 


10          20 


30          40          50  60          70          80          SO         100         110 

H.T.  Feeder  Loud  in  Amperes 


FIG.    2. OPERATION  OF  A  TWO-PHASE  DISTRIBUTION  SYSTEM. 

erased.  With  conditions  on  the  feeder  such  that  the  phase  curves  assume 
the  positions  E  and  F  it  would  be  necessary  to  retain  both  curves  and  op- 
erate each  phase  by  the  curve  corresponding  to  it.  All  the  curves  start 
at  120  volts,  which  represents  normal  pressure  at  the  customer's  cut-outs. 

With  a  hand-regulated  feeder  the  operator  reads  the  load  on  each 
phase  and  by  consulting  the  curves  finds  at  what  pressure  the  feeder  should 
be  operated.  When  the  load  changes  he  raises  or  lowers  the  pressure  to 
correspond.  When  automatic  regulators  are  installed  the  curve  is  used 
for  setting  the  contact-making  voltmeter  to  operate  at  normal  voltage  at 
the  balancing  points.  A  general  test  should  be  made  over  the  feeder  about 
once  a  month. 

It  has  been  suggested  that  small  shunt  transformers  be  installed  at 
selected  points  on  the  feeder  and  pressure  readings  taken  at  the  secondaries 
of  these  transformers  instead  of  at  the  customer's  cut-outs.  By  this 
method  the  actual  pressure  of  the  feeder  at  a  given  point  would  be  ob- 
tained. With  the  present  method  the  feeder  pressure  often  appears  to 
vary  on  the  same  phase  within  a  few  hundred  feet.  This  is  due  to  the 


OPERATION  OF  AND  CHANGES  IN  CIRCUITS 


81 


load  conditions  on  the  various  transformers.  The  writer  recalls  one  case 
in  which  there  were  three  customers  on  the  three  corners  of  a  certain 
street  fed  by  three  individual  transformers  connected  to  the  same  phase. 
Two  installations  were  being  supplied  with  current  at  120  volts,  while  the 
pressure  at  the  third  was  110  volts.  An  investigation  showed  that  the 
low  pressure  was  caused  by  the  aged  iron  of  the  distributing  transformer. 
The  scheme  of  using  the  small  independent  transformers  for  reading  the 
line  voltage  has  much  to  commend  it. 

Determining  the  Power-factor  of  a  Three-phase  Circuit  (By  C.  E. 
Howell). — Among  men  employed  by  operating  electric  companies  there 
are  many  who  know  that  methods  exist  by  which  the  power-factor  of  a 


| 

P< 

Cu 
wer 

ve 
Fac 

or 

J 

Line 
B 

( 

1 

100 

—  •'••• 

90 

^ 

i 

m 

VL 

H 

&4 

80 

/ 

/ 

Directions' 
Case  I:- 
Both  readings 
Positive  - 
Divide  Smaller  by 
;.  Find  this  Ratio  on 
Center  line  below. 
Drdinate  at  this  point 
an  with  curve  opposite 
ne  find  corresponding 
r  (above  50$). 

;  Negative. 
ve  reading.  Find  this 
ter  line  below.  Follow 
int  to  its  intersection 
n  center  line  find. 

5 
fe 

70 

/ 

/ 

, 

h 
CD 

•f 

_60 
50 

/ 

/ 

Larger  Reading 
Right  Side  of  ( 
Follow  up  the 
to  its  intersect! 
this  on  center  1: 
$  Power  Facto 
Case  II:- 
One  Reading 
Negative  by  Posit 
a  left  side  of  Cen 
rdinate  at  this  pc 
•ve  opposite  this  o 

Tw 

0 

Load 
Wms.o'n 

a 

»* 

OH 

C 

ircu 

t 

i 

^ 

/ 

/v 

PU 

30 

^s 

3 

20 

Divide 
Ratio  01 
up  the  o 
with  cu] 

^^ 

^ 

atio 

—  Wm.  Heading 

+  \v'm.  Reading  10 

-10^ 

P< 

ff^ 
P 

^ 

1-  -. 

5V-.5   -.4    -.3    -.2    -.llo 

A  *   i  , 

1      i      ,      . 

,           , 

r° 

1 

_ 

£ljatio 

^corresponding  $  Power  Factor   (Below  50$) 
-f-  Smaller  Wm.Reading  +  Larger  Wm.Reading. 

FIG.    1. CHART  OF  INSTRUCTIONS. 


three-phase  circuit  or  installation  may  be  determined,  but  comparatively 
few  are  able  to  apply  them  successfully.  Many  errors  made,  in  meter 
connections  due  to  the  effect  of  low  power-factor  on  the  registration  of 
single-phase  watt-hour  meters  (or  wattmeters)  or  separate  elements  of 
polyphase  meters  on  three-phase  circuits  are  directly  traceable  to  the 
lack  of  knowledge  of  the  points  brought  out  in  the  accompanying  illustra- 
tions. Figs.  1  and  2  are  copies  of  instruction  sheets  furnished  by  one 
operating  company  to  its  employees  where  induction-motor  installations 
are  the  rule.  These  sheets  have  been  reproduced  here  with  the  hope  that 
some  seeker  after  knowledge  will  be  benefited.  Fig.  1  in  the  well-known 
power-factor  curve  for  two  single-phase  meters  on  a  polyphase  circuit. 
It  also  gives  a  small  diagram  of  simple  connections  in  addition  to  a  few 


82 


HANDBOOK  OF  ELECTRICAL  METHODS 


words  of  instruction  with  reference  to  the  use  of  the  curve.  As  the  figure 
stands  it  should  be  self-explanatory.  Fig.  2  gives,  first,  a  method  of 
checking  results  obtained  by  employing  the  curve  given  in  Fig.  1,  as  well 
as  a  diagram  of  the  connections  to  be  used  in  obtaining  data  for  the  check. 
This  part  of  Fig.  2  should  be  easy  to  apply.  The  second  part  of  Fig.  2 
gives  a  detailed  method  of  determining  the  correct  connections  of  two 
single-phase  meters,  or  one  polyphase  meter,  on  a  three-phase  circuit. 
If  this  part  of  Fig.  2  is  employed  with  care  errors  in  meter  connections  on 
three-phase  circuits  clue  to  the  power-factor  being  near  50  per  cent, 
should  be  a  minimum. 


METHOD  OF  DETERMINING  THE  POWER  FACTOR 
/  ine  OF  A  3  -PHASE  CIRCUIT. 

ABC       FIRST:-Obtain  the  load  in  kilowatts  from  the  two 
'fefa 


m 


Load 

TmWaffmeters 
3  ^  Circuit 


SECOND :- Obtain  the  S-Phase  Current  of  the 
Circuit  by  qddjng( directly)  the  reading  of  the 
Ammeter  in  $  A"  to  that  of  the  Ammeter  in 
<}>  C*  and  multiplying  the  sum  by .  866 . 
JHIRDj-Calculate  the  apparent  Loa4  by 
mu/tjplyinq  the  above  3-fhase  Current  in 
amperes  bytheYo/taqe  between  Phases 
arid  dividing  bylOOOi 

FOURTH  ^-Determine  fhePower  Factor  (in%) 
by  dividing  the  True  Load  (/f.W.)  by  the  Apparent 
Load  (/fra.)  and  mult/plying  by  I 00. 


Power  Factor  Above  or  Below  50% 
If  Induction  Motor  load,  throw  off  a// load  and  run  motors  light' 
The  Power  Factor  will  be  below  50%,  and  one  Wattmeter,  or 
Element  ofa  polyphase  meter,  should  read  negatively.  Now 
load  up  circuit  to  within  20  %>  of  Total  Capaciry.  The  Single  - 


Phase  Wattmeter,  orflements,  which  read  negatively  on7/qht 
load  shou/d  now  read  positively  but  not  as  high  as  meter;  or 
Element,  which  gave  a  positive  reading  on  light  foad.  If  the 
Meters,  or  Elements,  are  connected  properly]  they  shov/d 
fulfill  the  above  conditions. 

NOTE;-  This  is  based  on  the  fact  that  on  "no-foad  "the  Power 
Factor  of  an  Induction  is  below  50%  . 


FIG.    2. CHART  OF  INSTRUCTIONS. 

To  illustrate  the  use  of  the  above  instructions,  an  actual  case  will  be 
taken:  A  100-h. p.,  three-phase,  440-volt  induction  motor  was  operating 
on  30  per  cent,  full  load  or  40  h.p.  (29.8  kw.)  at  60  per  cent,  power-factor 
(afterward  determined)  when  an  order  "came  through"  to  place  a  poly- 
phase meter  on  the  installation.  Immediately  after  the  meter  had  been 
connected  in  circuit  the  following  question  was  asked :  "Should  the  light 
element  add  to  or  subtract  from  the  heavy  element;  that  is,  is  the  power- 
factor  above  or  below  50  per  cent.?"  As  the  meter  leads  were  incased 
in  pipe,  these  could  not  be  traced,  therefore  the  instructions  in  the  second 
figure  pertaining  to  this  point  were  applied.  The  connected  load  of  the 
motor  having  been  thrown  off,  it  was  found  that  one  element  of  the 
meter  gave  a  negative  reading.  Sufficient  load  was  then  put  on  to  bring 
the  motor  to  about  80  per  cent,  of  its  full-load  rating.  Each  element 


OPERATION  OF  AND  CHANGES  IN  CIRCUITS 


83 


of  the  meter  (taken  separately)  now  read  positively,  but  the  element 
which  on  no-load  gave  a  negative  reading  on  80  per  cent,  load  read  lower 
than  the  heavy  element.  The  meter  had  been  correctly  connected  when 
installed.  Later  both  methods  given  in  the  above  figures  to  determine 
the  power-factor  of  a  three-phase  circuit  were  applied  and  both  gave 
approximately  60  per  cent,  (at  30  per  cent,  load),  as  previously  stated. 

Polyphase  Feeder-regulator  Motors  Operated  from  Single -phase 
Feeder  Circuit. — It  is  quite  generally  known  that  a  three-phase  motor 
operating  on  a  single-phase  system  will  supply  three-phase  energy  at  its 
terminals.  The  principle  has  been  applied  by  the  Kansas  City  Electric 
Light  Company,  of  Kansas  City,  Mo.,  in  one  of  its  substations.  During 


Single-Phase        Feeder  Circuits 
2300  Volts 


»  110  Volt 
j   3-Phase 
To  Automatic  Feeder-Regulator  Motors 

1-Phase,  05  H.P.  Induction  Motor 
with  3-Phase  "Winding 


FIG.    1. POLYPHASE  FEEDER-REGULATOR  MOTORS  OPERATED  FROM  SINGLE- 
PHASE  FEEDER  CIRCUIT. 

light  loads  the  frequency  changer  in  one  of  the  electric-service  company's 
substations  is  shut  down,  and  single-phase  energy  is  supplied  over  a 
single-phase  tie-line  from  another  substation.  The  frequency  changer 
when  operating  supplies  two-phase  energy,  which  is  distributed  to 
single-phase  feeder  circuits  in  such  a  way  as  to  maintain  a  balanced 
system. 

As  the  automatic  feeder-regulator  motors  require  polyphase  current 
for  operation,  an  induction  motor,  connected  as  shown  in  the  diagram, 
is  employed  to  furnish  three-phase  energy  when  the  frequency  changer 
is  shut  down.  Although  rated  as  a  0.5-h.p.  single-phase  machine,  the 
motor  is  equipped  with  three-phase  windings.  A  step-down  trans- 
former supplies  the  energy  needed  for  the  motor.  A  resistance-react- 


84 


HANDBOOK  OF  ELECTRICAL  METHODS 


ance  starter  is  connected  between  the  motor  and  one  of  the  low-tension 
terminals  of  the  transformer  for  starting  on  single-phase  energy.  With 
the  arrangement  shown  in  Fig.  1  it  would  be  possible  to  operate  the 
apparatus  from  a  distance. 

Interchangeable  Connections  for  Feeder  Resistance. — In  order  to  get 
the  same  pressure  on  direct-current  mains  near  the  station  as  in  outlying 
sections  supplied  over  comparatively  long  feeder  lines,  some  engineers 
have  actually  gone  to  the  point  of  carrying  a  1,000,000-circ.  mil  cable 
half  the  length  of  one  of  the  longer  feeders  and  then  back  again  to  the  mains 
near  the  station,  in  this  way  obtaining  the  desired  drop  in  voltage.  A 
scheme  of  making  the  feeder  resistance  adjustable  inside  the  station  itself 
is  employed  by  the  Kansas  City  Electric  Light  Company,  which  has 
made  good  use  of  some  standard  railway  grid  resistors  in  equipping  a 
short  heavily  loaded  feeder  that  terminates  within  75  ft.  of  the  station 
bus. 

Securing  the  largest  railway  grid  resistors  to  be  had  and  neglecting 
their  intermittent  rating  for  car  use,  special  tests  made  showed  that  these 
grids  would  carry  100  amp.  continuously.  Pairs  of  these  grids  were  then 
permanently  paralleled,  and  groups  of  fifteen  such  pairs  mounted  in  racks, 


No.  00  Wf  res 


Jumper  Arrangement  for 
Two-Thirds  Resistance. 


Jum 
Full 


u 


Ifor 
tance. 


1,000,000  C.M. 

(iWr 

-H^rPaU  100-Amp. 
Otrid  Resistors 
Paralleled 


FIG.    1. INTERCHANGEABLE  CONNECTIONS  FOR  FEEDER  RESISTANCE. 


one  thirty-grid  group  being  provided  for  the  positive  side  and  a  similar 
group  for  the  negative,  as  Fig.  1  shows.  By  means  of  the  jumper 
wires  and  lugs  used  with  the  diverter  grids  on  the  cars  any  adjustment 
from  full  to  two-thirds  of  full  resistance  can  be  obtained.  The  arrange- 
ment of  jumpers  for  these  two  conditions  is  illustrated.  At  full  load  the 
75-ft.  1,000,000-circ.  mil  feeder  thus  equipped  carries  1000  amp.,  and  the 
drop  across  the  resistance  banks  is  about  10  volts.  With  all  resistance  in, 
the  resistance  of  the  grids  about  equals  the  resistance  of  1000  ft.  of  1,000- 
000-circ.  mil  copper  cable,  so  that  the  terminal  pressure  on  this  short  line 
is  about  equal  to  that  on  the  other  full-length  feeders,  the  shortest  of 
which  is  1000  ft.  The  resistor  grids  are  mounted  in  the  basement  of  the 
Fifteenth  Street  direct-current  substation  without  any  special  provision 
for  carrying  off  the  heat  developed. 


OPERATION  OF  AND  CHANGES  IN  CIRCUITS 


85 


Rearrangement  of  Three -wire  System  to  Reduce  Voltage  Fluctua- 
tions.— In  a  Kansas  flouring  mill  operated  by  220-volt,  three-phase 
motors  trouble  was  experienced  with  the  flickering  of  the  lamp  circuits 
supplied  from  the  same  feeders  as  the  motors.  As  first  installed,  the 
transformers  were  arranged  to  furnish  220-volt,  three-wire  service  from 
a  single  phase  of  the  three  available.  The  10-kw.  transformers  were  pro- 
vided with  middle  taps  and  these  were  first  used  as  the  neutral  connec- 
tions of  the  110/120-volt,  three-wire  system  for  the  lighting  service. 
With  the  15-h.p.  motor  fed  from  the  same  lines,  the  lamps  flickered 


2300V. 


2300V, 
10  Kw.    10  Kw. 


2300V. 


AWVMMAJ 
AVWWVWi      rvVyVWVW\       rA/WWVVVi 


440V. 


150  Lamps 


No.  2 


15  Hp.  Motor 


440V. 


No.  2 


FIG.    1.  -  REARRANGEMENT  OF  THREE-WIRE  SYSTEM  TO  REDUCE 
VOLTAGE  FLUCTUATIONS. 


badly  each  time  the  motor  was  started  and  stopped  or  underwent  a 
change  in  load.  Connections  were  then  changed  to  the  arrangement 
shown  in  the  diagram.  Fig.  1,  the  three-wire  system  being  converted 
to  110/220- volt  service,  with  the  "outside  wires"  taken  from  new 
quarter  points  midway  between  the  original  neutral  and  the  outside 
motor  circuits.  In  place  of  the  220-volt  lamps  formerly  used,  110-volt 
lamps  were  installed.  The  result  has  been  the  practical  elimination  of 
the  flicker  that  was  formerly  so  objectionable,  probably  owing  largely 
to  the  fact  that  the  low-voltage  filaments  have  greater  heat-storage 
capacity  and  thus  are  less  sensitive  to  voltage  variations  than  the  220- 
volt  lamps. 

Circuit  with  Shifting  Neutral  Improved  by  Installation  of  Auto- 
transformer  (By  O.  H.  H-utchings). — A  somewhat  novel  use  was  made  of  a 
standard  lighting  transformer  by  the  writer  to  overcome  a  troublesome 
condition  that  developed  in  a  village  adjacent  to  Dayton,  Ohio.  The 


86 


HANDBOOK  OF  ELECTRICAL  METHODS 


village  receives  its  electric  service  from  the  Dayton  Power  &  Light 
Company,  a  local  three- wire  distributing  system  being  supplied  from  one 
25-kw.  transformer  centrally  located.  A  moving-picture  theater  is 
located  within  the  village  at  a  point  approximately  500  ft.  from  the 
transformer,  the  result  being  to  displace  the  neutral  at  such  times  as 
the  machine  would  be  in  operation,  the  machine  taking  its  current  at 
110  volts.  The  first  thought  was  to  install  an  independent  transformer 
at  a  point  near  the  troublesome  service,  but  this  necessitated  an  extension 
of  the  6600- volt  primaries  and  did  not  seem  justified.  The  plan  adopted, 
which  worked  out  satisfactorily,  was  to  hang  an  independent  transformer 
(5  kw.)  on  the  pole  from  which  this  service  connection  was  made  and 
connect  the  secondary  coil  across  the  outer  wires  of  the  theater  service. 
The  neutral  connection  of  the  three-wire  service,  leading  to  the  theater, 


Service 
3-W.110-220-V. 

Transformer 


5-K.W. 

Transformer 
Compensator 


FIG.    1. — CIRCUIT  WITH  SHIFTING  NEUTRAL  IMPROVED  BY  USE  OF  AUTO-TRANS- 
FORMERS. 

was  removed  from  the  distributing  lines  and  connected  to  the  neutral 
point  of  the  transformer  secondary,  using  the  transformer  as  a  "  com- 
pensator." The  primary  leads  of  the  transformer  were  carefully  taped 
on  account  of  the  higher  voltage,  the  transformer  being  connected  to 
11  step-up."  Tests  upon  this  service  after  the  installation  of  the  trans- 
former disclosed  the  fact  that  the  equipment  could  be  overloaded 
approximately  400  per  cent,  at  100  volts,  with  a  neutral  displacement  of 
only  1  per  cent.  The  diagram,  Fig.  1,  presents  this  scheme  clearly. 

Application  of  Tirrill  Regulator  to  Adjust  Balancer  for  Neutral  Regula- 
tion at  Distant  Point. — The  unbalancing  action  on  the  11 0-220- volt 
Edison  three-wire  system  of  the  Dayton  (Ohio)  Lighting  Company  is 
unusually  severe  owing  to  the  presence  on  the  lines  of  several  large  110- 
volt  elevator  motors.  A  90-kw.  balancer  set  is  provided  to  adjust  the 
voltage  differences  on  this  direct-current  system,  the  load  on  which  varies 
from  1000  kw.  to  1800  kw.  This  balancer  has  its  fields  adjusted  by  a 
Tirrill  regulator,  the  control  of  which  can  be  effected  from  any  one  of 


OPERATION  OF  AND  CHANGES  IN  CIRCUITS 


87 


fourteen  sets  of  pressure  wires  brought  back  from  as  many  points  in  the 
downtown  network,  so  that  the  neutral  pressure  can  be  kept  practically 
constant  at  this  given  point,  regardless  of  the  load  on  the  lines  or  the 
pressure  at  the  station.  Several  other  means  were  attempted  in  the 
effort  to  solve  this  voltage  variation,  the  severity  of  which  was  such  that 
use  of  a  three-wire  generator  had  to  be  abandoned  except  as  a  220-volt 
machine  feeding  into  the  outers.  The  present  application  of  the  Tirrill 
regulator  principle  is  due  to  0.  H.  Hutchings,  general  superintendent  of 
the  Dayton  system,  and  has  resulted  in  practically  perfect  regulation. 
The  opposed-voltage  relay,  energized  through  pilot  wires  from  the  point 
oji  the  network  regulated  for,  closes  in  the  corresponding  direction  when 
either  side  drops  in  pressure,  operating  one  of  the  contact  switches 


Direct-current 


Point  of 
Regulation 


Three-wire  Feeders 


Relay 


Pressure  Wires 


Contact  Switches 

FIG.    1. APPLICATION   OF  REGULATOR  TO  ADJUST   THREE-WIRE   BALANCER  FOR  DISTANT 

POINT  IN  NETWORK. 

which  short-circuits  the  corresponding  field  rheostat,  boosting  the  pressure 
on  that  side.  As  the  result,  a  very  close  voltage  regulation  is  obtained 
on  the  downtown  network, 'regardless  of  the  varying  unbalanced  loads. 

Where  pressure  wires  are  not  available,  it  may  be  suggested  that  a 
similar  regulation  for  a  distant  point  could  be  obtained  with  apparatus 
entirely  within  the  station  by  using  differentially  wound  relay  coils, 
having  one  winding  across  the  mains  at  the  bus  and  the  other  bridged 
across  a  shunt  in  the  outgoing  feeders,  in  this  way  obtaining  an  artificial 
subtractive  action  for  the  drop  in  the  feeders. 

Arrangement  of  Tirrill  Regulator  to  Compensate  over  Adjustable 
Range  of  Terminal  Pressures  (By  L.  S.  Smith). — When  a  Tirrill  field  regu- 
lator is  arranged  with  compensating  elements  to  deliver  a  uniform  pressure 
at  the  distant  end  of  a  transmission  line,  regardless  of  load,  it  is  some- 
times desirable  to  raise  or  lower  the  delivered  voltage,  depending  on  the 
regulator  to  maintain  this  new  voltage  value  constant.  The  5000-kw. 
steam  plant  of  the  Pueblo  (Col.)  Traction  &  Lighting  Company  transmits 
to  distant  substations  at  which  it  often  becomes  desirable  to  raise  the 


88  HANDBOOK  OF  ELECTRICAL  METHODS 

pressure  beyond  the  value  normally  held  by  the  generator  regulator. 
Without  disturbing  the  compensating  resistance  and  reactance  settings 
on  the  regulator,  this  is  accomplished  by  inserting  a  rheostat  in  series 
with  the  alternating-current  magnet.  The  rheostat,  as  built  by  Mr. 
M.  G.  Lord,  of  the  Pueblo  plant  staff,  for  use  with  a  Tirrill  regulator,  com- 
prises 50  ft.  of  No.  22  German-silver  wire  tapped  out  to  ten  contact 
points  on  a  face  plate.  This  little  rheostat  thus  permits  a  total  range  of 
about  20  per  cent,  of  the  delivered  pressure,  the  latter  voltage  being  held 
constant  as  before  at  any  value  for  which  it  is  adjusted.  Fig.  1  shows 
the  layout. 


A.C.  Magnet 
of  Regulator 

FIG.     1. ARRANGEMENT    OF    TIRRILL     REGULATOR     TO    COMPENSATE    OVER    ADJUSTABLE 

RANGE  OF  TERMINAL  PRESSURES. 


Voltmeter  Test  Boxes  at  Distribution  Points. — At  each  of  the  thirty 
distributing  centers  of  its  alternating-current  system  the  Kansas  City 
Electric  Light  Company  has  made  provisions  for  getting  graphic  records 
of  the  voltage  regulation  obtained.  Special  1-kw.  transformers  at  each 
of  these  distinguishing-point  poles  have  their  secondaries  wired  down  to 
connection  clips  in  a  permanent  instrument  box  mounted  on  the  pole 
6  ft.  above  the  ground.  The  interiors  of  these  boxes  have  rests  to  hold 
standard  portable  curve-drawing  voltmeters,  which  can  be  connected  up 
and  thus  left  in  position  to  draw  their  own  records  twenty-four  or  forty- 
eight  hours  at  a  time.  The  boxes  are  covered  with  sheet  metal  and  are 
provided  with  stout  padlocks  to  protect  them  against  tampering.  They 
are  also  well  up  and  out  of  the  way  of  pedestrians,  but  can  easily  be 
reached  by  the  instrument  man  with  the  aid  of  a  chair  or  box.  With 
the  aid  of  the  station  instruments  corresponding  to  the  same  feeds,  a 
close  check  is  obtained  on  the  compensation  necessary  for  each  feeder's 
regulation. 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS 

Installation,  Metering  Power,  Remote  Control  Circuits,  Interruption 
Records,  Testing,  Synchronizing  Bank,  Etc. 

Supporting  Cables  in  Vertical  Runs  (By  C.  L.  Wilson). — The  accom- 
panying Fig.  1  shows  a  method  for  supporting  l,000,000-circ.-mil  cables 
in  undergoing  a  vertical  rise  of  about  50  ft.  The  circular  clamping 
blocks  are  turned  out  of  maple  and  afterward  paraffined  thoroughly. 
The  inner  opening  of  the  blocks  is  given  a  diameter  the  same  as  the 
cable  itself  at  one  end,  tapering  slightly  to  a  larger  diameter  at  the  upper 
end.  U-bolts  threaded  on  each  leg  and  locked  to  the  angle-iron  framing 
with  nuts  serve  to  clamp  the  blocks  together  on  the  cable.  An  annular 
recess  is  groo.ved  on  the  outside  surface  of  the  blocks  to  receive  this  metal 


B— U-Bolt 


FIG.     1. CLAMPING  BLOCK  FOR  SUPPORTING  VERTICAL  CABLE. 

shank.  As  shown  in  the  magnified  diagram,  the  blocks  are  placed  with 
the  inside  taper  so  arranged  as  to  grip  the  cable  all  the  tighter  under  the 
weight  of  the  cable  itself  or  should  there  be  any  tendency  for  it  to  slip. 
This  little  "kink"  of  the  inside  taper  will  be  found  well  worth  the 
trouble,  for  it  secures  a  rigid  stationary  position  of  the  cable,  insuring 
a  construction  that  will  not  sag. 

Casting  Bolts  in  Concrete  Walls  (By  A.  McCarty). — In  mounting 
high-tension  switches,  busbar  frames,  barrier  slabs  and  other  parts  on 
concrete  walls  the  job  will  be  far  more  permanent  and  workmanlike  if 

89 


90 


HANDBOOK  OF  ELECTRICAL  METHODS 


during  the  pouring  of  the  concrete  the  bolt  studs  are  cast  directly  into 
the  wall  material  itself.  This  can  best  be  done  as  shown  in  the  accom- 
panying Fig.  1,  in  which  template  holes,  at  the  distances  and  positions 
of  those  in  the  future  fitting,  are  shown  bored  in  the  form  used  to  mold 
the  concrete.  Then  through  these  holes  are  clamped  the  bolts,  inclosed 
in  pieces  of  pipe  a  little  larger  than  their  own  diameter,  and  having  their 
far  ends  bent  into  a  partial  hook,  against  which  to  tighten  the  nut. 
When  the  concrete  has  hardened  and  the  forms  are  removed,  the  cleanly 
threaded  bolts  are  left  firmly  imbedded  in  the  wall  in  position  for  the 
attachment  of  fittings.  The  purpose  of  using  the  pipe  to  inclose  the  bolt 
is  to  allow  a  little  play  of  the  bolt  for  slight  variations  in  the  distances 


Wooden 
Forms 


mm    Threaded 
*V.-i>/.ail  I     and  Bent 


Three-quarter 
inch  Pipe 


,y,|   i  _  Concrete 
ir  Mixture 


CLAMPING  BOLTS  IN  CONCRETE  WALLS. 


between  holes  in  the  templates  or  fittings.  If  a  1/2-in.  bolt  is  inclosed 
in  a  3/4-in.  pipe  an  adjustment  of  1/4  in.  is  possible  at  each  bolt,  the 
shank  being  easily  sprung  into  the  position  desired.  The  pipe  also  forms 
a  shoulder  against  which  to  lock  the  form  template  when  clamping  on 
the  nut  before  pouring  the  form. 

A  Method  for  Bending  Busbars  (By  J.  Cloyd  Downs). — The  writer 
has  had  much  work  to  do  on  various  sizes  of  copper  busbars.  As  far 
as  possible,  lengths  of  approximately  20  ft.  were  used  as,  of  course,  the 
longer  the  individual  bars  the  smaller  the  percentage  will  be  that  is 
wasted  in  the  laps.  Copper  busbars  of  this  length  are  quite  difficult 
to  handle  and  to  bend  with  any  degree  of  accuracy  without  special 
apparatus.  In  doing  this  work  the  writer  has  found  a  comparatively 
easy  and  simple  way  to  bend  the  busbars.  This  consists  in  using  a 
piece  of  timber  about  6  in.  or  8  in.  and  perhaps  16  ft.  long,  and  arranging 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS  91 

a  clamp  at  one  end  made  up  of  a  piece  of  flat  iron  and  a  couple  of  bolts 
passing  through  the  timber.  The  busbar  is  secured  under  this  clamp 
within  about  2  in.  of  where  the  bend  is  desired,  and  a  pinch  bar  is  clamped 
to  it  as  shown  in  the  accompanying  Fig.  1.  With  this  apparatus 
the  busbar  can  be  bent  with  a  fair  degree  of  accuracy  to  any  angle 
desired.  Before  making  a  bend  a  wire  can  be  bent  to  the  correct  angle 
and  then  used  as  a  templet  in  bending  the  busbar.  To  put  a  quarter 
twist  in  a  busbar,  the  latter  is  clamped  and  a  pinch  bar  is  clamped  to 
it  at  right  angles  to  the  length  of  the  busbar  and  the  busbar  twisted. 
In  a  2  1/2-in.  by  1/2-in.  copper  busbar  a  quarter  twist  can  be  made  in 


FIG.    1. A  METHOD  FOR  BENDING  BUSBARS. 

about  6  in.  of  length  without  forging.  A  short  bar  can  probably  be 
handled  to  better  advantage  in  a  vise.  To  bend  a  bar  on  its  edge  it  is 
generally  necessary  to  send  it  to  a  forge  shop  and  to  make  the  bend 
while  the  bar  is  hot,  since  it  is  difficult  to  make  the  busbars  stay  flat 
otherwise. 

A  Switchboard  Wiring  Pit  (By  Edgar  M.  Thurber). — Wiring  around 
switchboards  in  stations  of  small  capacity  is  not  always  as  neatly  and 
systematically  installed  as  it  might  be.  Frequently  the  feeder  con- 
ductors are  brought  to  the  board  from  above  and  even  if  they  are  neatly 
arranged  they  obstruct  the  light  and  constitute  a  lodging  place  for  dust. 
Leads  from  generators  usually  are  carried  in  ducts  beneath  the  station 
floor  and  rise  to  their  lugs  on  the  switchboard  panels  from  below.  This 
is  a  neat  arrangement  and  it  at  once  suggests  to  the  small-station  de- 
signer that,  under  favorable  conditions,  it  is  best  to  bring  all  conduc- 
tors to  a  switchboard  from  below  rather  than  from  above. 

When  circumstances  are  such  that  it  is  feasible  to  bring  wiring  to 
panels  from  below  it  can  readily  be  arranged  for  in  buildings  not  having 
basements  through  the  construction  of  a  " wiring  pit"  like  that  in  Fig.  1, 
page  92.  The  pit  is  excavated  to  a  depth  of  from  4  ft.  to  5  ft.  at  the 
time  the  building  is  erected.  It  has,  in  the  example  shown,  brick  walls 


92 


HANDBOOK  OF  ELECTRICAL  METHODS 


and  a  concrete  floor.  In  Fig.  1  the  conductors  from  the  generator  and 
the  exciter  sets  are  conveyed,  in  wrought-iron  conduit,  beneath  the  floor, 
from  the  machine  terminals  to  the  wiring  pit.  Four  feeders  (Fig.  2) 
enter  the  pit  through  vitrified  underground  conduit  and  three  more 
enter  from  above  through  vertical  wrought-iron  conduits  secured  to 


Underground 
onduit 


Wiring 
Section    B-B 


FIG.    1.  -  WIRING  PIT  BACK  OF  SWITCHBOARD. 

the  face  of  the  station  wall  with  pipe  straps.  Within  the  wiring  pit 
all  of  the  conductors  are  supported  in  porcelain  cleats,  held  on  wooden 
battens  arranged  on  the  pit  walls,  as  illustrated  in  Fig.  3.  The  cleats 
(see  detail  in  Fig.  3)  are  of  the  single-wire,  split  type  and  are  clamped 
into  position  with  wood  screws.  The  battens  are  secured  to  the  pit  walls 
with  lag  screws  turning  into  wooden  plugs  inserted  in  the  brickwork. 
A  temporary  floor,  shown  in  Fig.  1,  is  provided  over  the  pit.  It 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS 


93 


consists  of  sections  of  such  size  that  they  can  be  readily  handled.  These 
sections  are  supported  on  a  timber  framework  (Fig.  1).  A  trapdoor  is 
located  in  one  corner,  so  that  the  pit  can  be  entered  without  the  necessity 
of  removing  an  entire  floor  section.  A  slot,  extending  the  entire  length 
of  the  pit,  at  the  side  adjacent  to  the  switchboard,  permits  the  conductors 


}"1"I     Underground 
ft  jjj^  ConJuit  Wall  of  Building^ 


Underground 
Conduitv 


FIG.    2. — ARRANGEMENT  OF  WIRING  IN  PIT. 

to  be  carried  vertically  upward  to  their  respective  lugs  on  the  panels. 
As  indicated  at  detail  "A,"  Fig.  1,  a  strip  is  nailed  along  the  edge  of  the 
section-supporting  timber  to  retain  the  floor  sections  in  their  proper 
locations. 

In  Fig.  4  is  shown  the  method  used  in  constructing  the  entrances 


Screw 
Hole 


Side  Elevation 
Details  cf  Cleat 


•  ;'•  ';•  i-  ?;.'•': : '.'. >  v, '.  ''• :  •  'it  •*•.'"• '  •  -K:  •'.  :J  '-•  ^  • '  '  •  i  ^  '•  • 


Method  of  Wiring  in  Pit 
FIG.    3. — METHOD  OF  SUPPORTING  CONDUCTORS  IN  PIT. 

of  the  underground  conduits.  The  vitrified  conduit  extends  only  about 
half  through  the  wall  and  a  portion  of  the  inner  wall  is  chamfered  all 
around  at  an  angle  of  about  30  deg.  to  meet  the  edge  of  the  conduit. 
The  wall  face  is  thus  formed  so  that  the  conductors  entering  the  pit 
through  the  conduit  will  not  have  to  be  bent  sharply  where  they  leave 


94 


HANDBOOK  OF  ELECTRICAL  METHODS 


the  conduit,  as  they  would  have  to  be  if  the  end  of  the  conduit  length 
were  flush  with  the  true  inner  surface  of  the  wall.  Sharp  bends  must 
be  particularly  avoided  where  lead-sheathed  conductors  are  involved. 
Where  the  wrought-iron  conduits  conveying  the  generator  and  exciter 
leads  enter  the  pit  the  wall  is  similarly  recessed,  as  detailed  in  Fig.  5. 

In  arranging  the  wiring  within  the  pit  all  conductors  should  be 
carried  around  the  walls,  as  shown  in  Fig.  2;  none  should  be  permitted 


FIG.    4. WALL  FACE  AT  VITRIFIED  CONDUIT  ENTRANCE. 

to  cross  it,  except  at  the  ends.  This  procedure  will  involve  more  copper 
than  if  the  most  direct  route  is  selected  in  each  case,  but  it  will  doubtless 
be  the  most  economical  in  the  long  run,  because  it  will  insure  ease  of 
inspection  and  will  leave  practically  the  entire  pit  unobstructed.  There 
should  always  be  ample  room  in  a  pit  for  the  wiremen  and  for  the  tackle 
used  in  drawing  conductors  into  the  conduits. 

Face  of  Wall 


FIG.    5. WALL  FACE  AT  IRON  CONDUIT  ENTRANCE. 

Colored  Wire  for  Switchboards  and  Panels. — Colored-braid  wire  is 
now  standard  for  switchboard-instrument  connections  in  the  stations 
of  the  Kansas  City  Electric  Light  Company  and  for  meter  circuits  in  its 
customers'  installations.  Red,  blue,  brown  and  yellow  are  used  to  indi- 
cate various  phases,  etc.,  No.  12  being  specified  for  series-transformer 
connections  and  No.  14  for  voltmeter  connections.  The  same  color  of 
wire  is  in  each  case  associated  with  the  same  phase  for  both  series  and 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS 


95 


shunt  connections,  so  that  when  connecting  up  a  polyphase  meter  it 
is  a  simple  matter  to  bring  similar  colors  to  similar  phase  binding  posts. 
On  any  given  switchboard  or  customer's  panel  the  nomenclature  is  iden- 
tical throughout.  The  same  rule  does  not  hold  between  different  instal- 
lations, but  the  order  of  phase  rotation,  which  is  of  chief  importance,  is 
always  the  same  for  all  boards  on  the  system.  Black  is  used  for  the 
common  return  unless  there  is  a  third  wire,  in  which  case  this  phase 
receives  a  yellow  wire.  Manufacturers  furnish  this  colored  wire  at  a 
cost  about  10  per  cent,  in  advance  of  regular  wire  prices.  The  scheme  is 
shown  in  the  diagram,  Fig.  1. 


Series  Transformers 
FIG.    1. COLORED  WIRE  FOR  SWITCHBOARDS  AND  PANELS. 

Connection  Board  for  Metering  Power. — The  diagram,  Fig.  1  on  page 
96,  shows  an  improved  arrangement  for  reading  the  current  in  three 
lines  using  only  one  ammeter,  as  well  as  for  reading  three-phase  watts 
with  only  one  single-phase  wattmeter.  The  board  is  " fool-proof" 
when  properly  wired  up,  and  it  is  difficult  to  make  an  error  in  connec- 
tions. No  interlocking  mechanical  parts  are  necessary.  The  number 
of  special  pieces  required  is  reduced  to  a  pair  of  raised  clips  which  convert 
the  double-pole  switch  into  a  triple-throw  connection.  The  three  single- 
pole  switches  serve  as  line  switches  and  as  ammeter-short-circuiting 
switches. 

If  the  three  lines  coming  from  the  source  of  power  are  connected  to  the 
three  terminals  at  the  top  of  the  board  and  the  load  is  connected  to  the 
three  terminals  at  the  bottom,  the  circuit  is  closed  by  using  the  three 


96 


HANDBOOK  OF  ELECTRICAL  METHODS 


single-pole  switches.  The  current  in  the  left  line  is  read  by  connecting 
the  ammeter  to  the  two  terminals  at  the  side  of  the  board  and  closing 
the  main  switch  to  the  left.  Opening  the  left  single-pole  switch  allows 
the  current  in  this  line  to  pass  through  the  meter.  Next,  by  closing  the 
single-pole  switch,  moving  the  main  switch  to  a  position  vertical  to  the 
board  so  that  it  makes  contact  with  the  raised  clips,  and  opening  the 
middle  single-pole  switch,  the  current  in  the  middle  line  can  be  read. 
For  the  current  in  the  third  line,  close  the  last  single-pole  switch,  move 
the  main  switch  to  the  right  and  open  the  right-hand  switch. 


FIG.    1. CONNECTION  BOARD  FOR  METERING  POWER. 

To  measure  power  with  a  single-phase  wattmeter,  the  current  coil 
of  the  instrument  is  connected  in  series  with  the  ammeter,  and  one  end 
of  the  potential  circuit  is  led  to  the  middle  terminal  at  the  top  of  the 
board.  The  other  potential  terminal  of  the  wattmeter  is  then  led  to  the 
left-hand  or  right-hand  line  corresponding  to  the  one  in  which  the  cur- 
rent coil  is  connected.  The  sum  of  the  two  readings  gives  the  total 
power  being  transmitted.  No  wattmeter  reading  is,  of  course,  taken 
with  the  current  coil  in  the  middle  line.  When  the  power-factor  is  less 
than  50  per  cent,  the  smaller  wattmeter  reading  will  be  negative  and 
should  be  subtracted  from  the  larger. 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS 


97 


The  connections  indicated  by  the  dotted  lines  are  made  on  the  back 
of  the  board.  Equipped  with  60-amp.  125-volt  switches  and  suitable 
terminal  posts  for  the  external  connections,  the  board  measures  12  in. 
by  20  in. 

Connections  for  Obtaining  Feeder  Voltage  Records. — The  switch 
structure  of  the  turbine  station  of  the  Laclede  Gas  Company,  St.  Louis, 
has  a  double  bus,  and  in  the  office  of  the  electrical  engineer,  Mr.  William 
Bradford,  are  corresponding  duplicate  recording-instrument  panels,  each 
with  a  Bristol  recording  voltmeter,  General  Electric  curve-drawing  watt- 
meter and  totalizing  kw.-hr.  meters.  As  only  one  bus  is  commonly  used 
in  operating,  the  instruments  on  the  other  are  available  for  studying 
individual  feeder  conditions.  For  taking  voltage  curves  of  each  of  the 
ten  single-phase  feeders  Hubbell  push  sockets  have  been  mounted  on 
the  rear  of  these  panels.  Suspended  from  the  switchboard  braces  and 
running  the  length  of  the  feeder  panels  is  a  conduit  line  with  condulet 
fittings  inclosing  similar  push  sockets  opposite  the  panel  sockets.  A 
double-ended  prong-plug  jumper  serves  to  make  the  connection  between 
panel  and  conduit  sockets.  The  conduit  line  ends  in  a  connection  to 
the  regular  voltmeter  plug,  so  that  a  continuous  record  can  be  secured 
of  any  feeder  by  plugging  from  the  voltmeter  to  the  corresponding  panel 
socket. 

Alarm  to  Indicate  Operation  of  Remote  Rectifier  Set. — Two  of  the 
seventy-five  lamp,  4-amp.  magnetite-arc  rectifier  sets  in  the  Vandevanter 


Rectifier 
FIG.     1. ALARM  TO  INDICATE  OPERATION  OF  REMOTE  RECTIFIER  SET. 

substation  of  the  Union  Electric  Light  &  Power  Company,  St.  Louis, 
had  to  be  mounted  in  the  basement  on  account  of  lack  of  space  on  the 
main  operating  floor.  Since  the  station  operator  could  not  make  sure 
that  the  rectifiers  were  working  properly  without  running  up  and  down 
stairs  at  intervals,  W.  A.  Yandell,  in  charge  of  substations,  arranged  the 
series-solenoid  alarm  circuit  of  Fig.  1.  As  long  as  the  rectifier  operates 
properly  the  white  lamp  is  lighted.  If  the  arc  circuit  is  interrupted  the 


98  HANDBOOK  OF  ELECTRICAL  METHODS 

contact  arm  drops  to  the  bell  circuit,  at  the  same  time  lighting  a  red 
lamp  as  a  visual  warning.  At  the  St.  Charles  Street  substation,  where 
a  number  of  rectifiers  are  banked  together  closely,  the  series  solenoids 
of  the  tube  circuits  are  arranged  to  ring  an  alarm  bell  in  case  of  any 
interruption.  If  an  arc  forms  between  the  auxiliary  electrode  of  the 
tube,  short-circuiting  and  causing  danger  of  overheating  of  the  exciting 
transformer,  the  alarm  is  similarly  sounded. 

Alarm  Circuit  for  Double-throw  Oil  Switches. — The  switchboard  of 
an  Eastern  power  house  was  recently  rearranged  to  provide  for  dupli- 
cate buses  onto  either  of  which  the  generators  could  be  thrown  by  means 
of  pairs  of  interlocked  oil  switches.  Later  a  circuit-breaker  alarm  and 

To  Bus  2 (Closed) 
To  Bus  l(Open) 

Pilot  Lamp 

ii  ii 

Switchboard 


;-;    ':  \  1 

JP 

Alarm 

-^ 

—  i-  — 

r 

5 

0      0 

FIG.    1. ALARM  CIRCUIT  FOR  DOUBLE-THROW  OIL  SWITCHES. 

pilot-lamp  scheme  was  applied  to  the  single-throw  switches  on  the  board, 
so  that  upon  the  opening  of  any  breaker  a  bell  would  ring  and  a  lamp  on 
its  panel  would  be  lighted.  To  extend  this  system  to  the  double-bus 
section  caused  the  station  wireman  some  worry,  because  one  switch  or 
the  other  of  each  interlocked  pair  would  be  open  at  all  times  and  yet 
the  bell  must  ring  if  for  any  reason  the  closed  member  opened.  The 
difficulty  was  solved  (see  Fig.  1),  double  contacts  being  provided  at  each 
switch  and  the  pair  connected  in  series.  The  oil  switch  which  is  open 
has  its  own  signal  contacts  closed.  Opening  of  the  other  switch  closes 
its  contacts  and  thus,  completing  the  circuit,  sounds  the  alarm. 

Remote  Control  of  Circuits  (By  D.  E.  King).— The  upper  Fig.  1 
on  page  99  shows  a  simple  device,  reliable  as  well  as  inexpensive,  for 
the  remote  control  of  either  primary  or  secondary  circuits.  The  write- 
prefers  this  scheme  to  solenoids  or  carbon  break  switches.  The  three- 
phase  motor  is  fed  from  a  No.  14  wire  at  a  potential  of  220  volts,  the 
distance  from  the  office  to  the  switch  being  a  quarter  of  a  mile.  The  oil 
switch  connects  the  2300-volt  primaries  with  two  series  transformers, 
used  for  street  lighting,  and  to  reverse  the  direction  of  rotation  of  the 
motor,  to  throw  the  circuit  on  or  off,  a  two-pole,  double-throw  switch 
is  used.  The  center  leg  of  the  motor  is  always  in  circuit  and  when  the 
switch  is  thrown  in  one  position  two  of  the  phases  are  reversed.  In 
the  other  position  the  connections  are  normal. 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS  99 


Oil  Switch 


Wooden  Fly  Wheel 


FIG.    1. REMOTE  CONTROL  OF  CIRCUITS. 


o 

Feeder 
No.l 


Resistance 


PI 

1  1 

—  *^ 

A 

MM 

- 

LL_I 

«-*- 

-—  - 

lw         01 

~i                   n 

O 

Feeder 
No.2 


Stop  Watch 


FIG.    1. — STOP-WATCH  RECORD  OF  SERVICE  INTERRUPTIONS. 


100 


HANDBOOK  OF  ELECTRICAL  METHODS 


Stop-watch  Record  of  Service  Interruption. — The  lower  Fig.  1  on  page 
99  shows  a  pair  of  relays  and  a  stop-watch,  which  preserves  an  accurate 
record  of  the  time  the  voltage  is  off  the  system.  A  device  of  this  kind  is 
now  being  used  by  the  Yonkers  (N.  Y.)  Electric  Light  &  Power  Company. 
Ordinarily,  the  relay  A  is  in  circuit,  and  it  remains  excited  as  long  as 
potential  is  on  the  feeder.  In  case  of  an  interruption  A  is  de-energized, 
allowing  its  weighted  armature  to  drop  and  deliver  a  slight  blow  on 
the  stem  of  the  stop-watch,  setting  the  timing  hand  in  motion.  Inci- 
dentally the  fall  of  the  armature  disconnects  at  a  the  circuit  to  relay  A, 
bridging,  instead,  the  relay  B  across  the  dead  feeder.  When  service  is 
restored  B  picks  up,  and  its  armature  in  closing  presses  on  the  watch 
stem  through  the  crank  arm,  this  time  stopping  the  moving  hand. 
Service  interruptions  are  thus  recorded  with  an  accuracy  down  to  one- 
fifth  of  a  second.  A  small  pilot  lamp,  P,  burns  as  long  as  relay  A  is  in 
circuit,  thus  indicating  at  a  glance  that  no  service  interruption  has  yet 
occurred.  This  little  2. 5- volt  lamp  is  supplied  with  energy  from  secon- 
dary windings  wrapped  on  the  frame  of  relay  A.  An  ordinary  8-c.p. 
lamp  is  used  as  resistance  in  series  with  the  relays.  By  means  of  the 
double-pole  double-throw  switch,  the  recording  device  can  be  connected 
to  either  one  of  two  feeder  lines  which  it  is  desired  to  supervise.  A  pair 
of  springs  hold  the  stop-watch  in  place,  minimizing  jarring  and  helping 
to  receive  the  blows  of  the  falling  weight  and  the  relay  movement. 

Field  Excitation  Test  Lamps. — A  useful  adjunct  to  the  operating 
equipment  of  a  large  Western  turbine  station  is  a  bank  of  lamps  and 


FIG.    1. FIELD  EXCITATION  TEST  LAMPS. 

switches  by  means  of  which  the  floor  attendant  can  determine  at  any  time 
which  machines  have  their  fields  excited.  The  small  lamps  of  the  bank, 
which  is  mounted  on  a  pedestal  at  the  center  of  the  turbine  room,  are 
each  connected  in  parallel  with  one  of  the  turbine  fields,  and  by  closing 
its  corresponding  switch  momentarily  the  operator  can  test  to  find  on 
which  units  the  excitation  switches  are  closed.  The  scheme  is  shown  in 
Fig.  1. 

Circular   Synchronizing  Bank   (By  F.    G.  Falloon). — The  following 
view.     Fig.    1     explains    the    connections    of  a    simple    synchronizing 


SWITCHBOARDS  AND  POWEfe 


101 


bank  made  of  twelve  ordinary  110-volt  lamps  with  the  necessary 
sockets  and  wiring.  If  the  incoming  machine  is  below  speed,  full 
voltage  will  revolve  about  the  circle  to  the  left.  If  the  machine  is 
above  speed,  full  voltage  will  revolve  to  the  right.  When  both  machines 
are  near  synchronism  the  two  opposite  points  of  the  diamond  will 
come  to  full  voltage,  followed  by  the  remaining  two  points.  When  all 
four  points  are  at  full  voltage  the  machine  is  in  synchronism. 


FIG.     1. CIRCULAR  SYNCHRONIZING  BANK. 

Relay  Auxiliary  Contact  For  Aluminum  Check  Cell. — The  exciter 
bus  is  connected  to  the  operating  bus  in  Sub-station  No. -5  of  the  Union 
Electric  Company's  system,  St.  Louis,  through  a  reverse-power  circuit- 
breaker  which  opens  in  case  of  any  reversal  due  to  shutdown  of  the  5- 
h.p.  motor-generator  set  commonly  energizing  the  combined  125-volt 
bus.  Bridged  across  the  operating  bus  is  also  an  80-amp.  storage  battery, 
provided  for  operating  the  oil  switches  in  case  of  interruption  of  direct- 
current  supply.  This  battery  is  arranged  with  an  aluminum-iron  check 
cell  containing  six  aluminum  and  seven  iron  plates  in  a  10  per  cent,  solu- 
tion of  boric  acid.  The  check  cell  alone  operates  very  satisfactorily 
in  preventing  flow  of  energy  in  the  reverse  direction,  but  was  found  to 
introduce  about  5  volts  drop  when  passing  current  normally.  This 
loss,  which  occasioned  local  heating,  has  now  been  prevented  by  adding 
a  relay  with  contacts  closing  across  the  check  cell.  For  reverse-direction 


102 


HAND3OOK,QF  ELECTRICAL  METHODS 


currents  the  circuit  is  still  open  as  before.  But  when  the  check  cell 
admits  current  in  the  normal  direction  the  relay  winding  is  thereby 
energized,  closing  the  path  around  the  cell.  The  relay  remains  closed 
as  long  as  energy  is  being  drawn  from  the  battery,  dropping  out  again 
when  the  current  falls  below  the  value  necessary  to  hold  up  its  armature. 
The  scheme  is  shown  in  Fig.  1. 


Relay 


80-Amp.-hour 
Battery 


Station 
Lamps 


Operating 
Bus 


Ll 


5-Hp.Mg. 


Exciter 


Bus 


Reverse  Current 
Breaker 

FIG.    1. RELAY  AUXILIARY  CONTACT  FOR  ALUMINUM  CHECK  CELL. 

Balancer  Set  used  to  bring  up  Low  Battery  Cells. — A  central  station 
supplying  energy  to  a  110-220-volt  Edison  three- wire  system  uses 
a  pair  of  50-kw.  machines  coupled  together,  for  operating  as  a  balancer 
set.  The  same  station  also  contains  a  storage  battery  with  a  rating  of 
1200  amp.-hr.  To  give  low  cells  special  charges  without  disconnecting 
them  from  the  main  battery  operation,  this  pair  of  balancer  machines 
proves  very  useful  when  run  as  a  motor-generator  set.  The  machine 
used  as  a  generator  is  carefully  insulated  from  ground  and  all  other 
parts  of  the  system,  and  can  be  connected  to  a  pair  of  No.  0  copper  leads 
extending  overhead  the  length  of  the  battery-room.  Jumpers  with 
clip  connectors  are  used  to  join  this  charging  circuit  to  the  terminals  of 
the  cell  or  cells  to  be  treated,  copper  strips  being  clamped  onto  the  lead 
webs  to  insure  good  contact.  With  this  arrangement  any  cell  or  group 
of  cells  can  be  put  through  a  cycle  of  charge  without  disturbing  its  con- 
nections or  the  operation  of  the  main  battery. 

Disconnect  Switch  for  Feeder  Regulators. — In  a  turbine  plant 
having  its  lighting  feeders  equipped  with  induction-type  regulators  use  is 
made  of  disconnect  switches,  like  Fig.  1,  page  103,  to  cut  the  regulators 
clear  of  their  circuits  so  that  they  may  be  repaired  or  inspected.  There 
are  three  single-blade  hook-type  switches  mounted  on  a  common  slate 
block  each  over  its  corresponding  regulators.  When  the  two  outer 
blades  are  closed  the  regulator  winding  is  in  series  with  the  line.  To 


SWITCHBOARDS  AND  POWER  HOUSE  DETAILS 


103 


disconnect  the  regulator,  its  rotor  is  first  brought  back  to  zero,  to  avoid 
short-circuiting  any  incremental  voltage,  and  the  middle  blade  is  then 
closed.  Opening  the  outer  blades  finally  disconnects  the  apparatus 
altogether,  rendering  it  "dead."  Meanwhile  the  feeder  may  continue 
in  uninterrupted  use. 


To  Feeder 


FIG.    1. DISCONNECT  SWITCH  FOR  FEEDER  REGULATORS. 

Extra  Eye  Lugs  for  Disconnect  Switches. — In  a  certain  railway 
substation  the  converting  equipment  consists  of  three  500-kw.,  600-volt 
rotaries  supplied  through  step-down  transformers  from  a  pair  of  25,000- 
volt  transmission  lines.  These  supply  connections  are  in  duplicate, 
so  that  if  one  line  breaks  down  the  load  can  be  transferred  to  the  other 
by  means  of  a  double  set  of  disconnecting  switches.  The  switches  have 
double  blades,  the  holes  for  the  puller  hook  being  drilled  through  two 
blades. 


Lug  Eye 


Bolt 


Hole  for 
Hook  Stick 


FIG.    1. EXTRA  EYE  LUG  FOR  DISCONNECT  SWITCHES. 

The  operators,  however,  experienced  difficulty  in  finding  the  holes 
quickly  when  necessary,  so  the  extra  eye  lugs,  Fig.  1,  were  added. 
Without  changing  the  switch  blades  in  any  way,  this  lug  fits  over  the 
blades  and  is  secured  by  the  threaded  bolt  passing  through  the  original 
hook-hole  in  the  blades. 

8 


104  HANDBOOK  OF  ELECTRICAL  METHODS 

Iron-pipe  Construction  in  Distribution  Rack. — During  a  general 
rehabilitation  of  the  plant  of  the  Elwood  (Ind.)  Electric  Light  Company 
the  distribution  rack  which  carries  the  outgoing  lines  for  local  lighting 
and  motor  service  was  reconstructed.  The  feature  of  this  rack  recon- 
struction has  been  the  use  of  3-in.  iron  pipes  with  porcelain  insulators 
fastened  between  them  by  means  of  bolts,  giving  to  the  finished  structure 
a  neat  appearance  combined  with  a  degree  of  stability  and  endurance 
not  possible  to  obtain  by  the  use  of  wooden  supports.  Wires  are  brought 
out  from  the  insulators  in  the  wall  of  the  station  to  the  two  lower  pipes 
and  are  there  dead-ended.  Jumper  wires  are  thence  run  to  the  insulators 
suspended  from  the  pipe  above  and  after  making  a  right-angle  turn  at 
this  point  are  taken  to  the  lead  which  they  are  to  supply.  Throughout 
the  installation  white,  brown,  blue  and  yellow  insulators  have  been  used 
to  distinguish  respectively  primary  circuits,  secondary  circuits,  arc- 
lamp  circuits  and  grounded  wires  so  that  a  man  working  on  the  rack 
has  little  trouble  in  distinguishing  the  several  classes  of  lines. 


VI 
SIGNS,  DISPLAY  LIGHTING,  SPECIAL  APPLICATIONS 

Operation,  Installation,  Protection   of   Signs,    Show-window  Lighting, 

Photography,  Etc. 

Remote -control  Switches  for  Flat-rate  Signs. — The  Topeka  (Kan.) 
Edison  Company  operates  a  number  of  flat-rate  signs,  turning  these  on 
at  dusk  and  off  at  10  o'clock,  except  Saturday  night,  when  they  are 
burned  until  11:30  p.  m.  When  controlled  and  switched  by  hand,  as 
formerly,  the  company  received  the  usual  complaints  because  one  sign 
was  turned  on  before  another  or  off  before  some  one  else,  as  the  patrol- 
man progressed  on  his  rounds.  This  unavoidable  dissatisfaction  is 
now  ended  and  the  wage  of  the  patrolman,  $20  per  month,  is  saved  by 
switching  all  the  signs  from  a  central  point  by  means  of  electromagnet 
contactors. 

Edison  Three-Wire  Mains 


*•>                                                       k        V 

Sign        | 

Sign 

000000 

ooooooooo 

_L  JL 
<r^ 

Controlling   <^\    ^ 

Carbon  Break  |    '    | 

Magnet    -^r-1 
Switch  ~~^f=-. 

<C_      ® 

dS 

•s^^* 

is  «^ 

100-Amp.  Leaf   X^g 
Spring  Contractor        c 

*"  Brass 

Rod 

Closed  to  ^<              ^^  "5  -55 

Shell-Type 
Eleccro  Magnet 

Operate:^^            -^^B,2 

T 

| 

Holding 

Sli-Jb.  No.25/- 

I 

Enameled  Wire 

.  ::..  I 

_i_                Pilot  Wire,  No.10  Iron 

110  Ohms. 

'/ 

\j 
Iron  Plunger 

FIG.    1. REMOTE-CONTROL  SWITCHES  FOR  FLAT-RATE  SIGNS. 

Shell-type  electromagnets  are  used  in  the  switches,  the  outer  dimen- 
sions of  the  magnetic-return  casing  being  4  in.  long  by  3  in.  in  diameter. 
The  plunger  has  1-in.  travel  in  the  1-in.  brass  tube  in  which  it  slides. 
Two  and  one-third  pounds  of  No.  25  black  enameled  magnet  wire  are 
used  in  each  coil.  A  brass  rod  connects  the  plunger  with  the  leaf-spring 
contactors,  which  are  supplemented  by  carbon  blocks  to  take  any  arcs 
that  form  on  breaking  the  circuit.  J.  E.  Gossett,  electrical  foreman,_who 

105 


106 


HANDBOOK  OF  ELECTRICAL  METHODS 


laid  out  the  scheme,  estimates  the  cost  of  these  magnet  switches  to  be 
about  $6  each. 

Extending  through  the  business  district  is  a  No.  6  iron  pressure  wire 
which  is  used  as  the  pilot  circuit  and  tapped  in  multiple  to  the  magnet 
windings.  Each  coil  has  a  resistance  of  about  110  ohms  and  at  110  volts 
takes  1  amp.  which  closes  the  contact  vigorously.  A  smaller  current 
will  hold  the  plunger  in  the  closed  position  so  that  the  control  point  is 
provided  with  a  predetermined  resistance  which  can  be  inserted  in  the 
pilot  circuit  after  the  switches  have  been  closed,  reducing  the  current 
per  coil  to  0.5  amp.  This  is  ample  to  hold  the  contacts  in  position. 
As  shown  in  Fig.  1,  to  light  the  signs  the  controlling  switch  is  closed, 
the  resistance  switch  having  already  been  closed.  The  latter  is  then 
opened,  inserting  resistance  to  cut  the  holding  current  down  to  normal 
value  so  that  the  magnets  will  not  heat.  A  master  clock  switch  controls 
the  sign  circuits,  avoiding  all  hand  manipulation.  Fifteen  large  signs 
are  now  operated  by  the  Topeka  pilot-wire  circuit,  which  is  nearly  a 
mile  in  length. 

Interchangeable  Illuminated  Sidewalk  Sign. — The  accompanying 
Fig.  1,  shows  a  simple  interchangeable  electric-lighted  sign  to  be  seen  in 
front  of  a  Kentucky  moving-picture  theater  where  the  bill  is  changed 


Heavy  Green 
Diffusing  Glaos 


Slide 


Brass 


Clear  Glass 


Polished  Brass  Frame 


Tl  Slide  (4  x  3-in.) 
I  with  Painted  or 
I— I    Pasted  Paper 
Letter 


r 


for  Removing 
Letter  Slides 


Brass  Strip 
(Polished) 


FIG.    1. INTERCHANGEABLE  ILLUMINATED  SIDEWALK  SIGN. 


nightly  and  the  sidewalk  announcement  must  be  varied  with  equal 
frequency.  There  are  two  2-ft.  by  3-ft.  panes  of  heavy  diffusing  green 
glass,  mounted  together  in  a  polished  brass  frame  with  sufficient  interval 
to  admit  the  half-dozen  lamps  which  light  the  display.  Across  the 
glass  panes  on  each  side  are  fixed  brass  rods,  and  extending  to  within 
about  4  in.  of  the  brass  frame  on  the  edges  -polished  brass  strips  are 
fastened  to  these  rods,  forming  slide- ways.  In  these  grooves  are  placed 
the  3-in.  by  4-in.  clear-glass  slides  on  which  are  painted  the  individual 
letters.  If  preferred,  paper  letters  can  be  pasted  onto  the  glass  slides 
and  used  interchangeably  to  make  up  the  words.  The  lamps  inside  the 


SIGNS,  DISPLAY  LIGHTING,  SPECIAL  APPLICATIONS 


107 


sign  are  lighted  through  an  extension  cord,  and  the  display  presents  a 
brilliant  appearance  lighted  from  both  sides. 

Running  Boards  for  a  Tungsten  Lighting  Installation  (By  Charles 
H.  Wales). — A  tungsten  lamp  installation  was  laid  out  for  a  building, 
shown  in  the  sketch,  Fig.  1.  With  the  best  arrangement  of  lighting 
units  it  was  found  that  one  row  lay  directly  under  a  large  galvanized- 
sheet-iron,  hot-blast,  heating  duct.  At  first  this  was  considered  a 
serious  obstacle  and  a  rearrangement  of  the  units  was  considered,  but 


Hot  Blast 
Heating  Pipes 


Roof  Truss 
Bottom 
Chord 


nnmg 

^^\.s 

^@ 

Fluted 

1       ^"L                1       JL- 

Reflector 

^^v. 

and 

^Tungsten 

Lamp 

Floor  Line  \^ 

Hot  Blast 
Heating 
/Pipe 


FIG.    1. SECTION  THROUGH  BUILDING. 


Wire 


FIG.     2. METHOD    OF    SECURING 

RUNNING  BOARD  TO  PIPE. 


the  scheme  indicated  in  Fig.  1  and  detailed  in  Figs.  2  and  3  was  finally 
adopted  and  has  given  entire  satisfaction. 

All  of  the  conductors  were  supported  on  porcelain  cleats,  which 
were  attached  to  running  boards  similar  to  that  shown  in  Fig.  4.  A 
running  board  was  clamped  to  the  bottom  of  the  heating  duct  with  a 
wrought-iron  strap.  The  middle  of  each  strap  (see  Fig.  3)  was  flat- 
tened for  a  distance  equal  to  the  width  of  a  running  board  and  drilled 
and  countersunk  for  1  1/2-in.  flathead  stone  bolts.  One  of  these  straps, 
which  had  previously  been  bent  to  a  circular  form,  the  circle  having  an 


Flathead 
Stove  Bolt 


IT  Running 
Punched        Board 
Washer 


FIG.    3. — SECTION  "AA7     OF  FIG.   2. 

internal  diameter  the  same  as  that  of  the  outside  of  the  heating  pipe, 
was  bolted  to  a  running  board  every  10  ft.  Ears,  as  shown  in  Fig.  2 
were  formed  at  the  ends  of  the  straps,  and  holes  drilled  therein  through 
which  the  clamping  bolts  were  inserted.  The  porcelain  cleats  were 
fastened,  but  not  set  up  tightly  to  the  boards  before  they  were  raised 
to  position.  The  straps  were  so  designed  that  the  distance  0,  Fig.  2, 
was  about  1  in.  after  the  bolts  had  been  set  up  snugly. 

Boards  and  straps  were  raised  to  position  and  clamped  to  the  pipe, 


108  HANDBOOK  OF  ELECTRICAL  METHODS 

the  wires  run  and  the  rosettes  put  on.  The  length  of  drop  cord,  from 
rosettes  on  the  running  board  on  the  pipe,  was  made  as  short  as  possible, 
as  it  was  desirable  to  have  the  lamps  hang  high.  Drop  cords  from 
the  other  running  boards,  attached  directly  to  the  roof  truss  chords, 
were  made  of  such  a  length  that  the  lamps  which  they  carried  were  the 
same  distance  from  the  floor  as  those  supported  by  the  running  board 
on  the  heating  pipe.  This  wTas  done  to  insure  an  appearance  oi  uni- 
formity and  to  prevent  objectionable  shadows  being  cast  by  the  hot- 
blast  pipe. 

In  Fig.  4  are  shown  details  of  the  running  boards  which  were  attached 
directly  to  the  roof  trusses  and  of  the  fittings  used  in  making  the  attach- 
ment. The  distance  between  centers  of  roof  trusses  was  so  great  that 

Running  Board  ^/Bolt 

Top  \\a3her  /  v 

Bottom  Chord  of  Truss 

/3L  JL_ 


Running  Board  in  Position  Washer 


Carriage  Bolt 


Top  View  of  Running  Board 


I!    o     II 

Detail  of  Detail  of 

Top  Washer  Bottom  Washer 

FIG.    4. DETAILS  OF  RUNNING  BOARDS  AND  FITTINGS. 

a  single  plank  was  not  sufficiently  stiff  to  carry  the  wires  and  fixtures 
without  excessive  deflection.  Accordingly,  each  board  was  reinforced 
with  another  plank,  which  was  clamped  to  the  first  with  carriage  bolts. 
The  second  was  arranged  vertically  as  indicated  in  Fig.  4.  The  built-up 
combination  was  of  ample  strength.  Each  vertical  reinforcing  plank 
was  so  sawed  that  it  was  somewhat  shorter  than  the  horizontal  one,  so 
that  it  would  not  interfere  with  the  bottom  chords  of  the  trusses. 

At  each  point  of  attachment  to  a  truss  a  top  washer  was  used.  This 
consisted  simply  of  a  piece  of  1  1/2  in.  by  1  1/4-in.  strap  iron  with  a 
hole  drilled  through  it.  It  prevented  the  nut  from  interfering  with  the 
slot  between  the  two  channels  forming  the  chord.  The  bottom  washer 
was,  as  detailed  in  Fig.  4,  a  piece  of  strap  iron  with  its  ends  bent  up. 
Each  bottom  washer  formed  a  rest  for  the  ends  of  two  adjacent  running 
boards.  With  the  boards  and  supporting  arrangement  in  position  the 
bolts  were  set  up  tightly  clamping  the  combination  firmly  in  position. 

Illuminated  Church  Sign. — Base-filament  glittering  electric  signs  which 
prove  so  attractive  for  commercial  institutions  sometimes  appear  inap- 
propriate for  church  use.  A  dignified  and  beautiful  illuminated  an- 


SIGNS,  DISPLAY  LIGHTING,  SPECIAL  APPLICATIONS 


109 


nouncement  is  erected,  however,  in  front  of  the  First  Baptist  Church, 
Dayton,  Ohio.  The  frame  is  of  simple  ecclesiastical  design  and  incloses 
two  art-glass  panels  in  rich  colors.  In  the  smaller  panel  above,  the 
name  of  the  church  is  permanently  fixed,  while  the  larger  glass  furnishes 
space  for  lettering  in  announcements  of  the  next  Sunday's  exercises. 
The  lamps  within  the  sign  are  controlled  from  a  switch  in  the  church 
vestry. 

Illuminated  Sign  using  Flaming-arc  Lamps. — The  accompanying 
Fig.  1  shows  an  arrangement  of  a  flaming-arc  illuminated  sign,  suggested 
by  C.  M.  Axford,  Chicago,  in  which  a  pair  of  lamps  are  used  to 
illuminate  the  letters,  and  at  the  same  time  to  light  the  sidewalk  and 
store  front  where  the  sign  is  installed.  The  proposed  construction  is 
made  clear  by  the  sketch.  The  two  flaming-arc  lamps  are  connected 


X 
3 


FIG.    1. ILLUMINATED    SIGN    USING    FLAMING- ARC    LAMPS. 

in  series  across  110  volts,  and  together  consume  about  1  kw.  The  signs 
should  be  black  letters  on  a  frosted  background,  or  vice  versa,  and  the 
sign  surfaces  should  be  inclined  about  10  deg.  to  the  vertical  so  as  to  be 
most  effectively  read  along  the  street.  Above  the  sign  spaces  are 
hinged  doors,  through  which  access  can  be  had  to  the  lamps  for  renewals. 
These  doors  should  be  provided  with  gutters  discharging  at  the  curb 
line.  The  street  end  of  the  box  should  be  closed,  or  may  be  used  for 
a  small  sign,  while  the  end  toward  the  building  should  be  left  open  and 
preferably  cut  away  as  shown  to  allow  light  from  the  lamps  to  reach 
the  windows  and  store  front.  For  this  purpose,  the  sign,  which  should 
be  about  10  ft.  in  length,  extending  to  the  curb,  should  be  mounted  at 
least  4  ft.  away  from  the  building  line,  being  suspended  irom  a  chain 
and  bracket  or  other  construction.  Opal  globes  on  the  flaming-arc 
lamps  will  tend  to  improve  diffusion  of  the  light  within  the  sign,  and 
minimize  " spotting"  of  the  letters.  The  use  of  an  illuminated  sign  of 
this  kind  is  suggested  in  positions  where  it  has  been  the  custom  to 
hang  a  pair  of  naked  flaming-arc  lamps  in  front  of  the  store,  depending 
on  them  to  light  the  front  and  windows  and  the  owner's  sign.  Under 


110 


HANDBOOK  OF  ELECTRICAL  METHODS 


such  conditions,  the  extreme  intensity  of  the  lamps  defeats  the  latter 
purpose,  causing  the  passers-by  rather  to  shield  their  eyes  instinctively 
from  the  glare.  The  sign  proposed  would,  on  the  other  hand,  show  the 
proprietor's  legend  to  advantage  along  the  entire  street,  besides  lighting 
his  sidewalk  and  windows,  all  at  a  minimum  electrical  expenditure. 

A  "Kink"  to  Save  Lamps  on  Series-multiple  Circuits  (By  G.  Zim- 
merman).— Where  only  direct  current  is  available  in  downtown  sections 
it  is  often  necessary  to  use  the  series-multiple  arrangement  of  low- volt  age 
tungsten  sign  lamps.  Such  connections  have  given  a  great  deal  of  dis- 
satisfaction and  annoyance  by  their  rapid  destruction  of  lamps  following 
the  burning  out  of  one  unit.  To  prevent  trouble,  the  first  lamp  should  be 
replaced  immediately  it  is  seen  to  be  extinguished.  In  many  large  roof 


-o 

-o- 

-0- 

-o- 

-o- 

O 

-o 

o 

o 

-o- 

-o- 

0 

o 

-o- 

o 

Sign 
Lamps 

-o 

O 

-o- 

-0 

o 
o 

•o 

-o 
o 

o 

0 

0 

o 

o 

O 

0 

0 

o 

o 

O 

0 

- 

O 

o 

- 

°" 

Auxiliary 
Sockets 

3 

-o- 

a 

;,          , 

-,'V 

FIG.    1. SAVING  LAMPS  ON  MULTIPLE  SERIES  CIRCUITS. 

signs  and  inaccessible  displays  it  is  out  of  the  question  to  get  ladders  and 
go  up  on  to  the  sign  after  dark  to  replace  a  single  lamp.  In  such  cases 
it  has  been  found  convenient  to  have  the  wires  from  each  group  of  small 
lamps  in  multiple  extended  down  to  two  or  more  sockets  mounted  in  the 
roof-house  or  other  easily  accessible  place.  These  sockets  should  be 
carefully  labeled  with  the  group  to  which  they  belong.  Then  as  soon 
as  a  lamp  on  the  sign  is  seen  to  be  out,  and  its  fellows  making  an  effort 
to  redivide  the  load  among  themselves,  it  is  only  necessary  to  insert  a 
new  lamp  in  one  of  the  auxiliary  sockets  of  the  same  circuit,  again  equaliz- 
ing the  current  flow  to  its  normal  value.  This  will  save  the  remaining 
lamps  of  the  group  as  well  as  the  operation  of  the  whole  display  itself, 
and  next  day  or  once  a  week  a  man  can  go  aloft  to  replace  the  accumula- 
tion of  burned-out  lamps.  The  remedy  shown  in  Fig.  1  is  inexpensive, 
only  one  wire  being  required  from  each  group. 

Electric-lighted  Showcase  for  the  Plate-glass  Storeroom  Door.— 
The  plate-glass  door  of  the  average  storeroom  occupies  valuable  display 


SIGNS,  DISPLAY  LIGHTING,  SPECIAL  APPLICATIONS 


111 


space,  of  which,  however,  little  use  is  ordinarily  made.  Realizing  this, 
an  astute  shoe  merchant  in  a  southern  Ohio  city  had  an  electric-lighted 
showcase  built,  as  shown  in  the  Fig.  1,  to  be  hung  behind  the  glass  door 
after  business  hours.  Connection  to  the  lamps  inside  is  made  by  a 
flexible  cord  which  can  be  plugged  into  an  outlet  at  the  side  of  the  door. 
A  couple  of  60-watt  tungsten  lamps  light  the  little  box  profusely,  and  the 
unique  display  draws  more  than  its  share  of  attention  from  the  passing 
public. 


FIG.    1. ELECTRICALLY-LIGHTED  SHOWCASE. 

Lighting  a  Chicago  Store  Window. — The  drawing,  Fig.  1  on  page  112, 
shows  the  show-window  illumination  adopted  for  "The  Hub,"  the  well- 
known  Chicago  department  store.  The  show  windows  are  lighted  by 
three  rows  of  lamps,  all  of  which  are  concealed  from  view.  These  are 
arranged  to  give  cross  lighting  and  thus  to  avoid  any  sharp  contrasts. 

Special  Ceiling  Surfaces  for  Indirect  Lighting  (By  G.  B.  Collier). — 
An  accomplishment  of  the  moving-picture  folk  in  improving  the  reflecting 
efficiency  of  their  projection  screens  should  offer  a  useful  hint  to  those 
designing  installations  of  indirect  lighting.  Having  brought  the  inten- 
sity of  the  arc  and  the  projecting  machine  up  to  its  practical  limit,  the 
moving-picture  men  next  attacked  the  problem  of  increasing  the  brilliancy 
of  their  pictures  from  the  screen  end,  seeking  a  material  of  higher  reflecting 
power  than  the  ordinary  sheeting  commonly  used.  A  picture  thrown 
on  canvas  can,  as  is  well  known,  be  seen  about  equally  well  from  the  rear 
of  the  screen  and  from  the  lantern  side,  indicating  at  once  an  efficiency  of 
only  50  per  cent,  in  either  direction.  If  part  or  all  of  these  rays  absorbed 
and  passing  on  through  the  sheet  could  be  returned  on  but  the  single 
useful  side,  the  illumination  of  the  picture  would  obviously  be  much 
increased.  This  result  has  recently  been  accomplished  in  the  production 
of  an  improved  screen,  heralded  on  the  billboards  of  the  5-cent  theaters 


112 


HANDBOOK  OF  ELECTRICAL  METHODS 


as  an  "  incandescent  curtain"  but  really  only  a  prepared  surface  of 
higher  reflecting  power  than  the  ordinary  white  screen.  The  results  are 
surprising,  the  pictures  being  far  more  brilliant  and,  as  a  result  thereof, 
less  subject  to  flicker. 

The   indirect-lighting   art   has   now   reached   the    same   limitation. 
Employing  reflectors  and  lamps  of  the  highest  efficiency,  the  over-all 


FIG.    1. LIGHTING  A  CHICAGO  STORE  WINDOW. 

results  are  yet  tremendously  reduced  by  the  poor  reflective  coefficient 
of  ceilings  and  walls.  The  character  and  tint  of  the  coating  applied  to 
these  surfaces  where  indirect  illumination  is  to  be  used  should  be  specified 
by  the  illuminating  engineer  as  a  part  of  the  lighting  system  and  not  left 
to  the  judgment  of  architect,  owner  or  painter,  whose  selection  is  made 
without  knowledge  of  the  duty  of  the  ceiling  as  a  reflector.  There  is 
no  doubt  that,  following  along  the  work  of  the  moving-picture  screen 
mentioned,  special  paints  could  be  developed  having  albedoes  or  reflective 
coefficients  much  higher  than  those  in  use.  With  such  paints  and  more 
of  the  light  returning  to  the  room  and  less  entering  the  walls  the  present 
excessive  wattage  required  with  indirect  lighting  (about  two  to  one 


SIGNS,  DISPLAY  LIGHTING,  SPECIAL  APPLICATIONS 


113 


compared  with  direct  illumination)  might  be  substantially  reduced  and 
the  physiological  comforts  of  this  system  of  lighting  be  more  generally 
secured. 

Danger  of  Broken  Lamp  near  Inflammable  Material  (By.  I.  Clyde).— 
The  accompanying  illustration  (Fig.  1)  shows  a  diagram  of  a  show  window 
lighted  by  tantalum  lamps,  the  breaking  of  one  of  which  caused  a  fire  re- 
sulting in  loss  both  of  life  and  property.  Two  shelves  were  joined  together 
by  a  sloping  board  surmounted  by  a  vertical  board  9  in.  high.  All  the 
shelves  and  boards  were  covered  with  cotton  wool  upon  which  were  dis- 
played celluloid  combs,  jewelry,  etc.  On  the  top  of  the  vertical  9-in.  board 


H 9—  — -J 

FIG.  1. DANGER  OF  BROKEN  LAMP  NEAR  INFLAMMABLE  MATERIAL. 

were  clamped  lamp  holders  arranged  so  that  the  lamps  would  be  at  right 
angles  to  the  board  and  projecting  over  it  into  the  window.  Where  the 
lamps  projected  the  cotton  wool  was  cut  away  in  a  circle.  In  all  there 
were  about  twenty  16-c.p.  tantalum  lamps  connected  two  in  series  across  a 
240-volt  circuit  by  means  of  flexible  wire.  The  lamps  were  spaced  about 
1.25  ft.  between  centers.  While  reaching  into  the  window  containing 
the  lighted  lamps  a  clerk  is  supposed  to  have  broken  one  of  the  lamps  and 
the  hot  filament  ignited  the  cotton  and  celluloid  and  within  a  minute 
the  whole  window  was  ablaze.  As  to  the  actual  cause  there  appears  to 
have  been  some  doubt,  but  experiments  conducted  subsequently  showed 
that  the  supposition  was  tenable  and  that  incandescent  lamps  installed 
under  the  conditions  mentioned  are  a  source  of  danger.  In  one  experi- 
ment a  lamp  was  suspended  a  distance  of  3  in.  over  dried  cotton  wool 
and  the  bulb  broken  by  a  hammer.  The  broken  filament  instantly 
ignited  the  cotton  wool  and  no  fuses  were  blown.  In  another  experiment 
a  lamp  was  suspended  3  in.  above  cotton  wool  thinned  out  on  which 
rested  a  celluloid  telephone  mouth-piece.  On  breaking  the  lamp  both  the 


114 


HANDBOOK  OF  ELECTRICAL  METHODS 


wool  and  the  celluloid  immediately  caught  fire.  The  incident  shows  the 
danger  of  bringing  flimsy  decorative  material  near  lamps,  especially  in 
unventilated  windows  where  the  heat  ordinarily  would  cause  the  material 
to  dry  thoroughly  and  make  it  more  of  a  menace  than  one  would  suppose. 
The  Underwriters  have  ruled  against  flexible  cord  in  show  windows,  and 
if  the  installation  has  been  made  in  accordance  with  the  rules  it  is  safe 
to  say  no  fire  would  have  resulted.  Persons  are  too  prone,  however,  to 
underestimate  the  amount  of  heat  given  off  by  an  incandescent  lamp. 
An  Electrical  Advertising  Novelty. — Near  one  of  the  Fifth  Avenue 
stations  of  Chicago's  elevated  loop  an  ingenious  projec ting-lantern 
advertising  sheet  has  been  arranged  to  attract  the  attention  of  those 


FIG.     1. ELECTRICAL  ADVERTISING  NOVELTY. 

waiting  on  the  platform  opposite.  Through  a  protected  opening  in  a 
window  the  lens  of  the  lantern  projects  its  rays  against  a  mirror  mounted 
several  feet  from  the  building  and  at  such  an  angle  as  to  reflect  the  image 
onto  a  screen  on  the  wall  below  the  window,  where  the  rays  come  to  a 
focus.  This  arrangement  is  made  clear  in  the  diagram,  Fig.  1.  Use  of  the 
reflecting  mirror  extending  beyond  the  building  avoids  the  necessity  for 
a  window  opening  equal  to  the  size  of  the  screen,  requires  less  room  in 
the  building  and  does  away  with  the  bright  spot  shown  by  the  lantern 
lens  when  the  stereopticon  is  placed  on  the  opposite  side  of  the  screen 
from  the  spectator,  as  would  otherwise  be  necessary.  Tendency  to  dis- 
tortion caused  by  the  angle  at  which  the  screen  intercepts  the  pencil  of 


SIGNS,  DISPLAY  LIGHTING,  SPECIAL  APPLICATIONS 


115 


rays  can  be  prevented  by  arranging  the  stereopticon  slide  with  a  swing 
back  paralleling  it  to  line  of  the  building. 

Influencing  the  Curio  Seekers*  Choice  Electrically. — When  the  pro- 
prieter  of  a  certain  little  curio  shop  in  the  city  of  Niagara  Falls,  N.  Y., 
wishes  to  push  the  sale  of  any  article  or  to  emphasize  the  presence  of 
any  timely  trinket  in  life  showcase  he  does  so  by  simply  changing  its 
position  in  the  case.  As  is  shown  in  Fig.  1,  auxiliary  illumination  is 


FIG.    1. INFLUENCING  CURIO  SEEKER  S  CHOICE  ELECTRICALLY. 

furnished  by  10-watt  tungsten  lamps  supported  by  extension  arms 
and  shades  so  as  to  throw  the  full  intensity  of  their  light  upon  the 
object  beneath  them.  Catching  the  eye  on  account  of  its  comparatively 
greater  illumination,  the  tourist's  attention  is  immediately  directed  to 
the  very  article  which  the  shrewd  shopkeeper  is  anxious  to  dispose  of 
first.  The  low  price  of  electrical  energy  in  the  Power  City  makes  it 
practicable  for  shopkeepers  to  burn  lamps  all  day  as  well  as  during  the 
evening  hours  in  places  where  illumination  will  increase  the  volume  of 
the  sales. 


VII 


LAMPS   AND    LIGHTING   CIRCUITS,  SIGNAL  BELL  CON- 
NECTIONS, ETC. 

Installation  and  Maintenance  of  Lamps,  Special  Installations,  Adapta- 
tions to  Special  Circuits,  Supervision  and  Control  of  Circuits 

Lighting  One  Lamp  on  Four-lamp  Fixtures  With  Three-wire  System. 
—The  method  employed  by  the  Kansas  City  Electric  Light  Company  for 
supplying  electricity  to  the  four  lamps  on  each  street  fixture  so  that  one 
lamp  may  be  operated  all  night  and  the  advantages  of  a  three-wire  system 
when  all  of  the  lamps  are  lighted  still  be  retained  is  interesting.  At  the 
2200-volt  distributing  board  in  the  central  station  are  a  double-pole  oil 
switch  and  a  single-pole  oil  switch  connected  as  shown  in  Fig.  1. 


as 

To  Source  of  Supply 


vTTci 


All  Nisht  Trans. 
2200-220  Volt  _ 


Oil  Switches 

Early  Evening 

Trans. 
-2200-220  Volt 


j-H!,,, 

r 

I 

r.- 

0 

^  §                                                      I 

<^-S 

_^  o 

J-3                                                     -1* 

-0- 

0- 

•2                                   I 

o  ' 

O? 

o                                    ^* 

°1  ' 

1 

i 

^>-All  Night  Lamp-_^ 

-0 

/ 

si 

-o 

1 

3i 

| 

•S1 

o-  ! 

ol 

0-  & 

0! 

0 

| 

To  WireN 

All  Night 
^  Lamp 


^220 

•110 


FlG.   1. LIGHTING   ONE    LAMP  ON  FOUR-LAMP  FIXTURES  WITH  THREE-WIRE  SYSTEM. 

Up  to  midnight  both  of  these  switches  are  closed;  after  that  time  the 
single-pole  switch  is  opened,  thereby  leaving  a  single  night  lamp  in 
service  until  sunrise. 

Two  single-phase  transformers  are  used  for  each  section  and  are  con- 
nected as  shown  in  the  diagram.  One  transformer  furnishes  the  energy 
for  the  lamps  which  are  lighted  till  midnight  (with  the  exception  of  the 
all-night  lamp) ;  the  other  transformer  furnishes  energy  for  the  all-night 

116 


LAMPS  AND  LIGHTING  CIRCUITS 


117 


lamp  only.  A  wire  connects  the  middle  of  each  secondary  and  is  grounded 
in  addition  to  being  connected  to  one  of  the  lines  running  along  the  top 
of  each  pole.  By  connecting  the  outer  wires  to  the  transformers  as 
shown,  220  volts  is  maintained  across  them  and  the  advantages  of  a  three- 
wire  system  are  thus  obtained.  The  middle  wires  on  each  side  of  the 
street  are  tied  together  where  practicable. 

Lamp  Protection. — In  gymnasiums,  hand-ball  courts,  indoor-tennis 
courts,  etc.,  tungsten  lamps  should  be  protected  against  the  chance 
impact  of  balls  thrown  by  players  by  installing  a  wire  screen  or  guard  of 
some  kind  around  the  lighting  units.  Frequently  the  mistake  has  been 
made  of  attaching  these  guards  to  the  lamp-holders  themselves,  with 
the  result  that  when  a  ball  struck  the  screen  the  jar  and  vibration  trans- 
mitted to  the  whole  fixture  was  sufficient  to  break  the  filaments.  The 


—  Uprights 
X-Ray  "Beehive" 


FIG.    1. — LAMP  PROTECTION. 

accompanying  Fig.  1,  shows  the  improved  method  of  supporting  the 
guard  screen  used  in  the  case  of  a  recently  completed  gymnasium  in 
which  the  protector  is  separately  mounted  entirely  clear  of  the  lamp 
fixture  and  reflector.  The  bottom  of  the  wire  basket  is  hinged  and  held 
closed  with  a  hasp,  to  give  easy  access  for  renewing  lamps  and  cleaning 
globes  and  reflectors. 

Rubber  Band  Prevents  Lamp  from  Backing  Out  (By  A.  T.  Vernon)  .— 
In  a  large  industrial  shop  near  Chicago,  which  is  lighted  by  500-watt 
tungsten  lamps,  trouble  has  been  experienced  from  the  vibration  of  the 
machinery  and  buildings,  causing  the  lamps  to  "back  out"  and  fall 
from  their  sockets.  After  several  lamps  had  become  unscrewed  and 
smashed  in  this  way,  the  experiment  was  tried  of  snapping  an  office 
rubber  band  over  the  threads  on  the  base.  When  the  lamp  is  screwed 


118  HANDBOOK  OF  ELECTRICAL  METHODS 

up  the  friction  of  this  rubber  causes  the  brass  cap  to  be  gripped  firmly, 
thereby  preventing  any  movement  that  might  allow  the  lamp  to  back 
out.  After  the  rubber  band  has  been  in  place  several  weeks  it  usually 
becomes  so  gummed  as  to  hold  the  base  all  the  tighter. 

Lamp-cord  Adjusters  (By  E.  E.  George). — The  following  device  has 
been  found  very  useful  for  droplights,  as  it  not  only  takes  up  the  slack 
in  the  cord,  but  permits  the  placing  of  the  lamp  at  almost  any  point  of 
the  room.  On  the  two  end  walls  of  the  room,  near  the  side  walls,  about 
7  ft.  or  8  ft.  from  the  floor,  fasten  four  hooks.  Through  these  hooks  run 
an  endless  cord  (chalk  line  is  very  serviceable).  This  cord  must  be  suf- 
ficiently slack  to  enable  it  on  one  side  to  be  looped  around  the  slack  of 
the  lamp  cord  and  on  the  other  side  to  be  doubled  through  a  Fahnestock 
connector  fastened  by  some  means  to  the  lamp  socket.  The  loop  through 
the  connector  can  be  shortened  or  lengthened  to  lower  or  raise  the  light. 
It  usually  takes  some  experimenting  to  determine  the  lengths  of  cord, 
and  also  of  lamp  cord,  that  will  give  best  results;  but  it  is  possible  so  to 
adjust  the  two  that  the  lamp  can  be  moved  almost  in  a  flare  all  over  the 
room.  The  lamp  will  stay  anywhere  it  is  placed. 

Holder  for  Removing  Street-series  Receptacles. — For  removing  and 
replacing  street  series  receptacles  the  line  department  of  the  Omaha 


Flange 


Series  Receptacle 

**~^ 
Bow  to  Handle 

FIG.    1. — HOLDER  FOR  REMOVING  STREET-SERIES  RECEPTACLES. 

Electric  Light  &  Power  Company  finds  that  the  home-made  U-bar 
device,  Fig.  1,  has  many  advantages  over  the  usual  pull-rope  extractor. 
The  holder  is  formed  of  two  U-bars  with  a  slot  between  them  wide  enough 
to  span  the  flange  on  the  porcelain  receptacle.  Working  in  the  slot  are 
a  pair  of  light  springs  which  grip  the  socket  just  firmly  enough  to  prevent 
it  from  falling  out  of  the  holder  while  being  lowered.  The  slot  itself 
holds  the  flange  firmly  against  any  vertical  movement.  A  long  wooden 
handle  is  attached  to  the  holder  through  a  spreader  bow  which  clears  the 
lamp. 


LAMPS  AND  LIGHTING  CIRCUITS 


119 


Cradle  Clamp  for  Hanging  Arc  Lamps. — The  cradle  used  for  hanging 
arc  lamps  which  is  shown  in  the  sketch,  Fig.  1,  has  proved  of 
great  value  in  installing  the  new  10-amp.  flame  lamps  at  Omaha,  Neb. 
These  lamps,  as  is  generally  known,  contain  an  annular  row  of  loose 
chemical  blocks  inside  the  casing  and  above  the  globe.  The  blocks  are 
laid  insecurely  in  place,  and  if  the  lamp  is  tilted  much  while  being  hoisted 
into  place,  one  or  more  blocks  may  become  dislodged  and  fall  into  the 
globe,  necessitating  lowering,  adjusting  and  hoisting  the  lamp  all  over 
again.  If  the  lamp  be  lifted  by  an  ordinary  rope  loop,  it  cannot,  of  course. 


Block 


FIG.    1. CRADLE  CLAMP  FOR  HANGING  ARC  LAMPS. 

be  hoisted  vertically,  and  even  if  hoisted  by  the  hanger  ring  it  will  in- 
variably be  tilted  while  being  pushed  over  and  transferred  to  the  perma- 
nent suspension  hook. 

The  rig  illustrated  was  devised  by  F.  Dickinson,  and  consists  of  a 
strap-iron  ring  hinged  so  as  to  open,  but  held  shut  to  clamp  the  lamp 
case  by  a  slip-ring  with  a  protective  collar  pin.  The  suspension  bale  is 
pivoted  to  the  hanger,  as  labeled  in  the  illustration.  The  snap  in  the 
center  is  of  help  when  first  placing  the  lamp  in  the  cradle.  The  lamp  can 
be  hung  on  the  hook,  which  holds  it  free  of  the  man's  hands  while  the 
clamp  ring  is  being  closed  and  made  fast.  The  whole  rig  is  then  hoisted 
to  the  proper  height,  turned  90  deg.  from  the  plane  of  the  paper  as  shown, 
and  while  held  vertically  with  care,  its  weight  supported  by  the  cradle,  is 
pushed  over  under  its  permanent  hanger  and  connected.  Use  of  this 


120  HANDBOOK  OF  ELECTRICAL  METHODS 

pivoted  device  has  enabled  the  work  of  hanging  the  lamps  to  proceed 
much  faster  and  has  saved  time  lost  in  lowering  and  replacing  lamps. 

Operation  of  Series  Alternating-current  Street  Arc  Lamps  (By  J. 
C.  Lawer). — All  municipal  arc-lighting  contracts  should  specify  the 
type  and  ampere  rating  of  the  arc  lamp  to  be  supplied.  In  addition, 
the  average  wattage  consumption,  number  of  hours  burned,  allowable 
outage,  etc.,  should  be  clearly  specified,  and  the  company  in  pursuance 
of  its  contract  should  make  a  periodic  statement  showing  the  operation 
of  its'arcs  in  detail. 

Two  municipalities  demand  sworn  monthly  reports  .(which  will  be 
described  later),  and  the  contract  specifies  that  series  7.5-amp.,  60-cycle 
alternating-current  arcs  are  to  be  supplied  and  that  the  average  con- 
sumption per  lamp  must  not  be  less  than  490  watts.  The  lamps  must 
burn  from  dusk  until  dawn,  which  is  considered  as  4000  hours  in  the  aggre- 
gate per  annum.  These  contracts  are  defective  in  many  ways  in  that 
some  agreements  had  to  be  made  afterward  in  regard  to  line  loss,  trans- 
former efficiency,  method  of  inspection  and  allowable  outage;  however, 
they  present  the  possibilities  for  a  new  contract  which  should  be  satisfac- 
tory and  free  from  any  future  misunderstandings. 

This  form  of  contract  affects  the  operating  department  and  it  must 
be  prepared  quickly  to  test  the  lamps  for  a  predetermined  wattage  and 
maintain  its  reports  in  a  systematic  manner.  The  following  methods 
and  appliances  have  been  adopted  by  an  operating  company. 

A  Convenient  Test  Board. — Fig.  1  is  a  wiring  diagram  for  an  arc- 
lamp  test  board.  The  right  end  is  arranged  for  connecting  two  alternat- 
ing-current series  lamps  and  the  left  side  for  three  alternating-current 
multiple  lamps.  The  indicating  wattmeter,  ammeter  and  voltmeter 
at  the  center  of  the  board  may  be  used  for  testing  one  lamp  at  a  time  of 
either  type  by  properly  operating  the  switches.  The  board  is  practically 
fool-proof,  and  it  is  impossible  to  connect  the  two  types  of  lamps  to  the 
instruments  at  the  same  time  so  as  to  do  any  damage.  The  double- 
pole  double-throw  switch  directly  below  the  instruments  controls  the 
potential  to  the  wattmeter  and  voltmeter  and  must  be  thrown  toward  the 
type  of  lamp  under  test.  On  the  multiple  side  the  supply  current  is 
preferably  controlled  by  a  double-pole,  single-throw  switch  protected 
by  fuses.  The  three  test  loops  for  the  multiple  lamps  are  each  controlled 
by  a  single-pole,  double-throw  switch.  Any  one  of  these  switches 
thrown  to  the  left  (away  from  the  instruments)  permits  the  lamp  on 
that  loop  to  burn  independently  of  the  instruments.  When  the  switches 
are  thrown  to  the  right  the  lamp  is  connected  to  the  loop  controlled  on 
the  instruments  unless  the  series  lamps  are  already  on  the  instruments, 
in  which  case  the  multiple  lamp  would  be  extinguished. 

The  series  circuit  is  supplied  by  means  of  a  six-lamp  constant-current 


LAMPS  AND  LIGHTING  CIRCUITS 


121 


transformer  through  a  bank  of  four  lamps  for  load.  There  are  two 
series  test  loops  controlled  by  two  single-pole,  single-throw  short-circuit- 
ing switches.  The  potential  for  the  voltmeter  and  wattmeter  is  controlled 
by  a  double-pole,  double-throw  switch  which  must  be  thrown  toward  the 
series  lamp  under  test.  The  series  lamps  may  be  thrown  off  or  on  the 
indicating  instruments  by  means  of  two  absolute  cut-out  hood  switches, 
which  form  the  principal  part  of  the  "  fool-proof "  device.  These  two 
hood  switches  are  placed  end  to  end  so  as  to  be  operated  by  one  handle 
or  lever;  the  lower  hood  switch,  as  shown,  has  the  short-circuiting  bar 


4  Arc  Load 


]  J 

J     Arcs 


Shelf 


Arc 
Repairs 


FIG.    1. CONVENIENT  ARC-LAMP  TEST  BOARD. 

removed  and  operates  as  a  two-pole,  single-throw  switch.  These  switches 
are  so  connected  that  with  the  lever  thrown  to  the  right  (away  from  the 
instruments)  the  series  lamps  are  short-circuited  from  the  instruments 
and  the  lower  switch  completes  the  multiple  circuit  through  the  instru- 
ments. When  the  lever  is  turned  to  the  left  the  series  circuit  by  means  of 
the  top  hood  switch  is  completed  through  the  instruments  and  the  multiple 
circuit  is  broken  by  means  of  the  lower  hood  switch.  One  test  circuit 
of  the  multiple  lamps  and  one  test  circuit  of  the  series  lamps  are  provided 
with  a  recording  wattmeter  and  short-circuiting  switch.  The  latter 
meter  should  be  adjusted  for  72  volts,  and  both  for  low  power-factors. 


122 


HANDBOOK  OF  ELECTRICAL  METHODS 


The  test  circuits  should  be  suspended  in  front  of  the  board  at  a  conveni- 
ent height. 

Methods  of  Testing  Alternating-current  Series  Arc  Lamps. — It  is  desir- 
able to  have  all  lamps  on  the  circuits  consume  as  near  a  predetermined 
rate  as  possible.  The  lamp  consumption  not  only  depends  upon  the 
internal  adjustment  of  the  lamp,  but  there  are  several  things  beyond 
our  control  which  must  be  allowed  for. 

Weather  affects  the  consumption  on  a  circuit  of  series  lamps  as  much 
as  10  per  cent.  This  is  principally  due  to  the  variation  of  temperature 
in  the  shunt  coil.  When  the  shunt  coil  is  at  a  low  temperature  and 
consequently  low  resistance  it  will  pull  a  shorter  arc,  thereby  reducing 
the  voltage  across  the  arc  with  a  resultant  lower  wattage.  The  series 
coil  is  not  perceptibly  affected  by  the  change  in  temperature,  as  the 
constant-current  transformer  maintains  it  at  a  constant  strength.  The 
line  loss  is  less  in  cold  weather,  and  where  this  loss  is  taken  at  a  constant 
percentage  the  lamps  must  be  operated  at  a  slight  percentage  above  the 
demanded  rating. 


b&U 

Aeon 

a 

t,   510 

/ 

x-" 

\ 

/ 

\ 

& 

w  500 

x^ 

—  ••- 

\ 

/ 

\ 

/ 

7^    * 

"verage" 

-497.-5-V 

1 

> 

~j*-—- 

-  •  y 

-y 

/ 

y 

..  ^—  —  ' 

^^ 

^_ 

^ 

/ 

s  4i° 

>    ._- 

/ 

«>J  460 

440 

0123456  789  10  11 

Hours  Bun 

FIG.    2. VARIATION  IN  WATT  CONSUMPTION  ON  SERIES  ARC  LAMPS. 


The  length  of  carbon  also  affects  the  consumption.  The  longer  the 
upper  carbon  the  heavier,  and  it  tends  to  produce  a  shorter  arc.  A  cir- 
cuit of  arcs  newly  trimmed  will  show  a  decided  decrease  in  consump- 
tion partly  caused  by  the  greater  weight,  but  principally  due  to  the 
low  resistance  of  the  carbon  tips,  and  even  while  the  arc  may  be  exces- 
sively long  the  consumption  will  remain  low.  It  requires  approximately 
forty  minutes'  burning  before  the  carbons  reach  a  normal  condition. 

Fig.  2  shows  the  variation  in  the  average  consumption  in  watts  on  a 
circuit  of  series  arcs  taken  for  a  continual  run  of  twelve  hours  with  prac- 
tically constant  outside  temperature.  It  will  be  noted  that  the  minimum 
occurs  when  the  lamps  are  first  turned  on  and  are  cold.  The  consump- 
tion increases  over  three  hours  as  the  lamps  become  warmer  and  as  the 
arc  becomes  longer  due  to  the  carbon  tips  being  consumed.  Between 


LAMPS  AND  LIGHTING  CIRCUITS  123 

three  and  four  hours  after  the  arcs  are  started  the  " feeding  point"  is 
reached.  Some  lamps  will  extinguish  themselves  for  an  instant  and 
start  at  a  low  consumption  as  the  feeding  takes  place.  Other  lamps  will 
feed  a  perceptible  amount  every  few  minutes,  probably  never  extin- 
guishing themselves,  and  will  operate  at  a  fairly  constant  rate.  It  is 
the  feeding  point  that  causes  the  watts  to  drop,  but  it  will  be  noted  that 
this  drop  is  not  as  low  as  at  the  original  starting  point.  The  continual 
heating  and  shortening  of  the  carbons  cause  each  successive  feeding  point 
to  reach  a  higher  consumption  than  the  preceding  one.  For  this  reason 
an  eight-hour  test  will  show  a  lower  average  consumption  than  a  twelve- 
hour  test.  The  high  consumption  caused  by  the  long-hour  burning  in 
winter  may  be  offset  by  the  colder  weather. 

As  eight  or  twelve  hours  is  too  long  for  a  practical  test  in  the  shop 
on  individual  lamps,  the  following  short  method  may  be  adopted  for  the 
7.5-amp.  and  6.6-amp.  lamps: 

The  lamp  should  be  trimmed  with  used  carbons  of  about  half  length 
and  allowed  to  burn  on  the  test  rack  for  at  least  forty  minutes.  It 
should  then  be  switched  on  the  indicating  instruments  and  the  short-cir- 
cuiting switch  thrown  in  for  an  instant  until  the  carbons  have  dropped  to- 
gether and  the  magnets  fallen.  The  switch  is  then  opened  and  the 
ammeter  is  noted  to  see  if  it  indicates  the  proper  amperage.  If  the 
lamp  under  test  is  of  the  7.5-amp.  type  the  indicating  wattmeter  should 
show  470  watts.  This  may  be  called  the  starting  wattage.  Then  the 
carbon  is  held  firmly  against  its  guide  and  at  the  same  time  the  series 
magnet  and  mechanism  pushed  down  until  the  clutch  can  take  a  new 
hold  of  the  carbon  at  as  low  a  point  as  possible.  The  mechanism  is  then 
released,  and  when  the  clutch  has  taken  hold  the  grasp  on  the  carbon  is 
released.  The  indicating  wattmeter  should  within  a  minute  read  510 
watts  to  515  watts.  This  is  the  " feeding  point"  and  the  lamp  should 
soon  drop  its  carbons  and  wattage.  This  test  requires  some  practice 
and  several  trials,  but  a  lamp  so  adjusted  will  average  from  495  watts 
to  505  watts  on  long-hour  burning. 

Nearly  all  new  lamps  are  fitted  with  a  clutch  stop  which  prevents  the 
globe  cap  from  melting  when  the  lamp  is  newly  trimmed  and  the  arc  is 
excessively  long;  however,  care  must  be  taken  to  see  that  the  bar  of  the 
stop  is  placed  sufficiently  high  to  prevent  the  clutch  from  striking  it 
before  the  feeding  point  is  reached.  The  bar  should  not  touch  the  clutch 
while  the  lamp  is  under  normal  running  condition. 

A  worn  clutch  will  permit  the  carbons  to  slide  together,  and  if  a  new 
clutch  is  placed  on  the  lamp  care  must  be  taken  that  it  shall  have  as 
much  play  and  grasp  the  carbon  like  the  old  one,  or  it  may  be  necessary 
to  readjust  the  entire  lamp. 

Method  of  Inspection. — Requiring  an  exceedingly  careful  supervision 


124 


HANDBOOK  OF  ELECTRICAL  METHODS 


of  its  street  arc  lamps,  one  company  placed  night  inspectors  on  regular 
routes  to  see  that  all  lamps  were  kept  burning.  These  inspectors  carried 
regular  night  watchman's  clocks  and  were  compelled  to  visit  certain 

SUMMARY  OF  MONTHLY  REPORTS 


Month 

Lamps  burned 
Hours    Minutes 

Net  watt- 
hours  con- 
sumed 

Number 
of  lamps 

Apparent 
lamp- 
hours 

Hours 
outage 

Net  lamp 
hours 

Per  cent, 
outage 

Watts 
per 
lamp 

January.  .  .  . 
February.  .  . 
March 

406         27 
345         11 
344         03 

53,833,860 
47,027,000 
46  895  510 

268 
270 
274 

108,579 
92,871 
93  923 

295 
352 
473 

108,284 
92,519 
93  450 

0.0027 
0.0038 
0  0050 

497.1 
503.3 
501   5 

April 

293         00 

40  401  930 

275 

80  431 

301 

80  130 

0  0037 

504   2 

May  
June. 

269         46 
239         36 

36,821,880 
32  999  100 

276 
276 

74,456 
66  130 

207 
1  0521 

74,249 

65  078 

0  .  0028 
0  0159 

494.5 
507  1 

July  
August  
September.  . 
October  
November.  . 
December..  . 

270         50 
309         15 
332         13 
375         09 
395         58 
424         31 

37,798,890 
41,324,478 
46,666,800 
50,983,740 
53,743,380 
58,056,840 

*"" 

276 
276 
276 
276 
276 
276 

74,750 
85,353 
91,692 
103,541 
109,287 
117,167 

161 
446 
481 
613 
682 
2.2811 

74,589 
84,907 
91.208 
102,928 
108,605 
114,886 

0.0021 
0.0052 
0.0053 
0.0059 
0.0062 
0.0195 

506.8 
486.7 
511.6 
495  .  3 
494.9 
505.3 

4,005          59  546,527,408  . 


!   l,098,180j    7,347       1,090,833    0.0067      501.0 


High  due  to  lightning  and  wind  storm. 


remote  stations  in  order  to  get  their  registering  keys.  They  made  two 
rounds  of  their  circuits  every  night  and  turned  in  their  clocks  to  a  super- 
visor every  morning  with  their  reports.  From  these  reports  the  lamp- 
hour  outages  are  obtained.  Following  is  an  arc  inspector's  report: 


Time  found 

Location 

Cause 

Lamp  hour  outage 

8  :  10 
8  :  30 
9  :00 

5th  and  A  St. 
9th  and  B  St. 
5th  and  A  St. 

Carbon  stuck 
Broken  inner  globe 
Carbon  stuck  chang- 
ing lamps 

1  hr.  10  min. 
1  hr.  30  min. 

40  min. 

Total  lamp-hour  outaee  . 

3  hrs.  20  min. 

A  lamp  is  considered  as  "out"  from  the  time  the  circuit  was  turned 
on  or  off  from  the  time  of  the  last  inspection.  This  record  enables  the 
supervisor  to  "spot"  a  lamp  which  continually  gives  trouble;  also,  the 
greater  number  of  actual  outages  found  prevents  the  company  from  hav- 
ing to  operate  its  burning  lamps  so  far  above  normal  in  order  to  maintain 
the  required  average  watt  consumption.  Experience  has  shown  that  a 
newly  trimmed  circuit  will  show  abnormal  outages. 

Following  is  a  form  of  monthly  arc-lamp  report  furnished  the  city : 

1.  Total  number  of  hours  burned 406  hrs.  27  min. 

2.  267  lamps  in  service  of  month,  lamp-hours 108,522 

3.  One  lamp  installed  27th,  lamp-hours 57 

4.  Total  apparent  lamp-hours 108,579 

5.  Total  lamp-hour  outages 295 

6.  Net  lamp-hours 108,284 

7.  Watt-hours,  primary 61,878,000 

8.  Watt-hours  at  lamps  (87  per  cent.) 53,833,860 

9.  Average  watts  per  lamp 497 . 1 


LAMPS  AND  LIGHTING  CIRCUITS 


125 


The  first  line  indicates  the  total  number  of  hours  the  lamps  were 
turned  on  during  the  month.  The  second  the  number  of  lamps  in  service 
the  first  of  the  month  multiplied  by  the  hours  burned,  giving  the  apparent 
lamp-hours.  The  third  indicates  the  lamp-hours  of  lamps  that  were 
installed  during  the  month.  The  fourth  is  the  sum  of  the  second  and 
third,  giving  the  total  apparent  lamp-hours  for  the  month.  The  fifth 
is  the  total  lamp-hour  outages  taken  from  the  night  inspectors'  reports. 
The  sixth  is  the  net  lamp-hours  burned.  As  to  the  seventh  line,  the 
recording  watt-hour  meters  were  necessarily  placed  on  the  primary  of 
the  constant-current  arc  transformer  and  were  agreed  to  have  an  efficiency 
of  94  per  cent.  The  line  was  entirely  of  No.  6  copper  and  the  loss  was 
originally  taken  according  to  the  C2R  losses.  This  came  so  near  a  con- 
stant percentage  that  the  combined  efficiency  of  the  line  and  transformers 
was  fully  agreed  on  as  87  per  cent.  Thus  the  eighth  line  shows  87  per 
cent,  of  the  seventh  line.  The  ninth  line  is  the  eighth  divided  by  the 
sixth  and  gives  the  average  watts  at  the  terminals  of  the  lamps. 

Owing  to  sudden  weather  changes  it  was  found  advisable  for  the 
supervisor  to  keep  his  report  practically  up  to  date  during  the  month  in 
order  not  to  run  short  or  be  far  above  the  required  watts  at  the  end  of 
the  month.  The  watts  could  be  changed  very  readily  by  making  a  slight 
adjustment  of  the  weights  on  the  constant-current  transformer,  which 
would  cause  scarcely  any  perceptible  variation  of  the  ammeter. 

Overcoming  Overload  on  Series  Arc -lamp  Circuits  (By  Charles  E. 
High). — It  sometimes  happens  in  planning  the  installation  of  a  series 

Lamps 

-X — X — X — X — X- 


Two-3  kw.  220  /440  Volt 
Transformers 


2200  Volt  Primary 


FIG.    1. OVERCOMING  OVERLOAD  ON  SERIES  ARC-LAMP  CIRCUITS. 

arc-lighting  system  that  sufficient  allowance  has  not  been  made  for  the 
future  growth  of  the  plant,  with  the  ultimate  result  that  the  constant- 
current  transformer  which  has  been  provided  becomes  overloaded. 
Many  times  this  overload  is  not  sufficiently  large  to  justify  the  expense 
of  securing  another  constant-current  unit.  This  was  the  case  with  our 
plant.  A  twenty-five-lamp  transformer  had  been  installed  with  the 


126 


HANDBOOK  OF  ELECTRICAL  METHODS 


plant  and  first  connected  for  60  per  cent.  load.  This  was  later  changed 
to  80  per  cent,  load,  then  to  full  load,  and  with  the  addition  of  still 
more  lamps  the  intensity  of  the  light  began  to  diminish.  To  overcome 
this  difficulty  the  scheme  of  Fig.  1  was  devised.  The  primaries  of 
two  3-kw.,  2200/440-volts  stationary-element  potential  transfomers 
were  connected  in  multiple  with  the  primary  of  the  constant  current 
unit,  and  the  secondaries  of  all  three  transformers  were  then  placed 
in  series  and  connected  directly  to  the  lamp  circuit.  This  plan  allowed 
the  operation  of  thirty-seven  lamps  on  a  twenty-five-lamp  circuit  and 
gave  satisfaction  in  every  way.  The  lamps  returned  to  their  normal 
brilliancy  and  no  transformer  was  heated  excessively.  The  constant- 
current  transformer,  operating  on  the  margin,  as  it  were,  and  maintaining 
the  current  at  6.6  amp.,  was  assisted  by  the  stationary  element  units, 
which  boosted  the  voltage  on  the  circuit  and  helped  supply  energy  to 
the  extra  lamps.  Care  must  be  exercised  in  making  the  connections 
that  proper  polarities  be  maintained  in  the  transformers. 

Lamp  Operation  Due  to  Accidental  Grounds. — Among  the  troubles 
recently  reported  to  an  Eastern  central-station  company  was  the  com- 
plaint of  one  customer  that  he  could  not  turn  out  part  of  his  lamps. 

Two-Phase  Primary 


.QQ&XL'i 
110 


no 


000 
MQflQ. 
UO 


110 


110 


Ground 


no 


Five  Wire  Secondary 

FIG.    1. LAMP  OPERATION  DUE  TO  ACCIDENTAL  GROUNDS. 

When  his  snap  switch  was  turned  "off"  the  lamp  candle-power  was 
simply  reduced,  the  filament  continuing  to  glow  dimly.  While  this 
case  was  being  investigated  another  customer  came  in  with  a  similar 
complaint  concerning  his  own  installation,  which  was  about  150  ft. 
distant  from  the  first.  Inspection  showed  that  although  both  custom- 
mers'  snap  switches  might  be  open,  the  lamps  would  burn  at  low  vol- 
tage. Furthermore,  it  was  found  that  this  energy  consumption  was  not 
being  recorded  on  either  meter.  With  one  switch  closed,  its  own  lamps 
would  burn  at  normal  voltage  and  candle-power;  meanwhile  the  second 


LAMPS  AND  LIGHTING  CIRCUITS 


127 


set  of  lamps  received  about  50  volts  and  could  not  be  turned  off  by  means 
of  their  own  switch. 

After  a  search  the  accidental  ground  of  the  first  installation  was 
located  in  a  fixture  which  had  been  hung  without  an  insulating  joint. 
In  the  second  case  the  ground  was  caused  by  abraded  insulation  where  a 
wire  passed  through  an  iron  post.  As  shown  on  page  126,  these  two 
grounds  completed  the  circuit  between  the  pair  of  220-volt  mains,  so 
that  while  both  single-pole  switches  were  open  the  pairs  of  lamps  were 
burning  in  series-multiple  through  the  ground  resistance.  It  so  happened, 
too,  that  the  grounded  side  in  each  case  passed  through  the  series  coils 
of  the  meter,  so  that  no  registration  was  made  of  the  current  continuously 
in  the  fugitive  circuit. 

Locating  Faults  on  Series  Lighting  Circuits  (By  Verne  James). — The 
usual  method  of  testing  dead  series  circuits  for  grounds  is  to  disconnect 
the  circuit  from  all  station  apparatus  and  then  to  connect  one  terminal 
of  a  magneto  test  set  to  the  circuit  and  the  other  to  ground.  If  the  bell 
rings  vigorously  when  the  crank  is  turned,  the  circuit  is  grounded.  If  it 
does  not,  the  circuit  is  clear.  If  the  circuit  is  very  long  or  in  cable  for  a 
considerable  portion  of  its  length,  the  bell  may  ring  even  if  the  circuit  be 


^    Temporary  Ground 
\     f       1 

Arc  Lamps 

X~  —          X          f    X             X           y 

B\k 

J         1 

2                   3  _^.__j____4                  5             Q 
Giound    J~T>~           a  y             y          \ 

Station           D  ^ 

X14 
I13 

8 
12                       11           10 

y                                  V                     V 

FIG.    1.  —  LOCATING  A  GROUND  ON  A  DEAD  CIRCUIT. 


clear  of  grounds.  The  method  of  locating  a  ground  on  a  dead  arc  circuit 
is  illustrated  in  Fig.  1.  Disconnect  all  station  apparatus  and  temporarily 
ground  one  side  of  the  circuit  as  at  B.  Proceed  out  along  the  line  and 
connect  some  testing  instrument  (a  magneto  test  set  is  most  frequently 
used)  in  series  with  the  circuit  at  some  point.  If  when  the  crank  is  turned 
the  magneto  bell  rings,  indicating  a  closed  circuit,  the  tester  is  between 
the  station  ground  and  the  ground  on  the  circuit.  If  the  magneto 
"  rings  open,"  the  tester  is  between  the  circuit  ground  and  the  ungrounded 
station  end  of  the  circuit.  If  the  test  set  is  inserted  at  lamps  1,  2  or  3, 
the  magneto  should  ring  "  closed,"  while  if  inserted  at  any  of  the  other 
lamps  it  should  ring  "open." 

In  locating  either  a  ground  or  a  break  on  a  series  circuit,  unless  the 
tester  has  an  idea  as  to  the  location  of  the  trouble,  he  should  proceed  to 


128 


HANDBOOK  OF  ELECTRICAL  METHODS 


the  middle  point  of  the  circuit  and  there  make  his  first  test.  This  first 
test  will  indicate  on  which  side  of  the  middle  point  the  trouble  is.  He 
should  then  proceed  to  the  middle  point  of  the  half  of  the  circuit  that 
shows  trouble  and  there  make  another  test.  This  will  localize  the 
trouble  to  one-quarter  of  the  circuit.  This  " halving"  of  the  sections  of 
the  circuit  should  be  continued  until  the  trouble  is  finally  found. 

A  ground  on  a  series  circuit  can  sometimes  be  located  with  the  current 
from  the  arc  generator  or  rectifier  by  placing  a  temporary  ground  on  the 
circuit  at  the  station.  For  example,  if  a  temporary  ground  is  connected 
to  terminal  B  and  the  device  that  supplies  the  operating  current  to  the 
circuit  is  connected  to  terminals  C  and  D  and  normal  operating  current 
thrown  out  on  the  circuit,  the  lamps  1,  2  and  3  will  not  burn,  indicating 
that  the  ground  is  between  lamps  3  and  4.  This  method  is  attended  by 
some  fire  risk,  hence  should  be  used  with  caution. 

A  method  of  locating  a  ground  on  a  series  circuit  with  lamp  bank  is 
suggested  in  Fig.  2.  A  bank  of  110-volt  incandescent  lamps,  each  of  the 

110    Volt  Incandescent 

/   Lamps. 


FIG.    2. LOCATING  GROUND  ON  A  SERIES  CIRCUIT. 


same  candle-power,  is  connected  in  series  as  indicated  and  one  end  of  the 
bank  is  permanently  grounded.  There  should  be  a  sufficient  number 
of  lamps  in  the  bank  so  that  the  sum  of  the  voltages  of  all  of  the  lamps  is 
at  least  equal  to  the  voltage  impressed  on  the  series  circuit  by  the  arc 
generator  or  the  regulator. 

In  locating  a  ground  the  flexible  cord  which  is  connected  to  the  center 
point  of  the  double-throw  switch  is  successively  placed  on  different 
points  on  the  conductor  that  connects  the  incandescent  lamps  in  series, 
the  switch  being  thrown  to  one  or  the  other  of  the  circuit  terminals  C  or 
D.  Move  the  flexible  cord  along  until  the  incandescent  lamps  in  the 
bank  between  the  point  of  connection  of  the  cord  and  the  permanent 
ground  burn  at  about  full  brilliancy.  When  this  condition  obtains  the 
voltage  impressed  across  the  lamps  that  are  burning  at  full  brilliance  is 
approximately  equal  to  the  voltage  impressed  on  the  portion  of  the  arc 
circuit  (to  which  the  switch  connects)  between  the  station  and  the  ground. 


LAMPS  AND  LIGHTING  CIRCUITS  129 

The  voltage  required  across  each  lamp  of  the  outside  circuit  being  known, 
the  number  of  lamps  between  the  station  and  the  ground  can  be  readily 
computed,  and  thereby  the  ground  is  located. 

For  example,  consider  Fig.  2.  There  is  a  ground  on  the  circuit  at  G. 
It  is  found  that  two  of  the  incandescent  lamps  of  the  bank  burn  at  full 
brilliancy  between  the  flexible  cord  connector  and  the  lamp-bank  ground. 
Since  1 10-volt  lamps  are  used  in  the  bank,  the  voltage  across  these  two  is 
220.  This  means  that  the  voltage  on  the  arc  circuit  between  points  C 
and  G  is  about  220.  Since  the  arc  lamps  each  require  about  50  volts, 
there  must  be  220-^50  =  4.4,  or  in  round  numbers  4,  arc  lamps  between 
C  and  the  ground  G.  After  making  a  test  with  the  switch  point  on  C, 
it  should  be  thrown  over  to  D  and  a  check  test  made  from  the  other  end 
of  the  circuit.  The  method  is  the  same  in  each  case. 

To  locate  a  break  in  a  series  circuit,  ground  one  end  of  the  circuit  at 
the  station,  as  in  Fig.  1.  Then  make  tests  at  different  points  out  on  the 
circuit  with  the  magneto  connected  in  between  line  and  ground.  So 
long  as  the  magneto  bell  indicates  a  closed  circuit,  the  open  is  on  the  line 
side  of  the  tester.  When  the  magneto  indicates  an  open  circuit  the  open 
is  toward  the  station  from  the  tester. 

Lamp  Signals  for  Hotel  Maids. — To  locate  housemaids  at  the  Hotel 
Radisson,  Minneapolis,  the  following  lamp  signal  system  is  used  by  the 
office  staff.  In  every  corridor  at  the  side  of  the  door  of  each  guest  room 
is  a  2-c.p.  incandescent  lamp,  and  on  the  wall  below  is  a  flush-plate  con- 
tact jack  into  which  on  entering  the  room  the  maid  inserts  a  plug  carried 
on  her  key  ring.  With  the  plug  in  place  the  little  lamp  over  the  door 
is  lighted,  indicating  from  any  point  in  the  corridor  in  which  room  the 
maid  is  working.  •  The  circuits  from  these  door  lamps  are  in  turn  grouped 
in  a  signal  board  in  the  hotel  office,  so  that  the  lighting  of  each  room 
lamp  is  indicated  by  its  corresponding  lamp  on  the  annunciator  board. 
If  a  certain  room  is  to  be  made  ready  on  short  notice,  the  maid  on  that 
floor  can  be  reached  by  noting  in  what  room  her  lamp  is  burning  and  then 
calling  the  corresponding  number  over  the  telephone. 

Lamp  Signal  System  for  a  Restaurant. — In  the  new  cafe  of  the  Boody 
Hotel,  Toledo,  a  row  of  fifteen  frosted  ball  lamps  is  mounted  over  the 
entrance  doorway.  Each  lamp  bears  a  number  corresponding  to  those 
of  the  waiters  on  duty.  After  delivering  his  order  to  the  chef,  the  waiter 
is  instructed  to  return  at  once  to  his  dining-room  station.  Then  as  soon 
as  the  food  is  prepared  the  kitchen  serving  man  closes  the  corresponding 
switch,  lighting  the  numbered  lamp  in  the  dining  room  and  calling  the 
waiter.  This  system  keeps  the  waiters  in  the  dining  room,  where  they 
can  give  attention  to  other  guests,  and  yet  causes  no  delays  in  prompt 
service  of  orders  when  ready.  The  position  of  the  lamps  enables  the 
waiters  to  watch  for  the  entrance  of  guests  while  awaiting  their  signals. 


130 


HANDBOOK  OF  ELECTRICAL  METHODS 


In  the  brightly  lighted  interior  the  operation  of  the  call  lamps  is  not 
obtrusive,  although  the  numbers  can  be  read  from  any  part  of  the  room. 
Lamp  Signal  System  for  Hospital. — An  electric-lamp  signaling  system 
without  solenoids  or  other  complications  is  used  in  St.  John's  Hospital, 
St.  Louis,  for  calling  nurses  and  attendants  to  patients'  rooms.  In  view 
of  the  fact  that  the  ordinary  bedside  cord  push-button  may  possibly 
injure  the  patient  by  shock  or  by  his  rolling  upon  it,  a  soft  linen  pull- 
cord  with  a  light  tassel  has  been  substituted.  A  slight  jerk  on  this  cord 
trips  out  a  contact  switch  in  the  wall  fixture,  completing  an  11-volt  cir- 
cuit which  lights  a  miniature  lamp  at  the  room  door,  another  in  the 


Superintendent's 
Annunciator  Lamp 

3 

Annunciator  Lamps 

oooooooo 

o  o  o  oo 
o  o  o  o  o 
o  o  oo  o 

oooooooo 
oooooooo 
oooooooo 

mi?fm°° 

l   [) 

1 

1 

\      1 

r 
i 

\^^Corridor  Lamp 

117 

Corridor 
Lamp 

Swl 

11  V 

/WWM 

110  Y. 

^ 

^ 

^ 

&                      ^ 

S^Trip  Wall 
^Switch 

K 

\^ 

s 

h 

1     Pull  Cord 

u 

1 

FIG.    1. LAMP  SIGNALS  FOR  A  HOSPITAL. 

annunciator  in  the  nurses'  quarters  and  a  third  in  the  superintendent's 
office.  The  lamp  by  the  door  is  designed  to  attract  the  nurses'  atten- 
tion is  she  should  be  passing  in  the  corridor  at  the  time.  Reproduction 
of  all  signals  in  the  superintendent's  office  affords  official  supervision 
of  the  promptness  with  which  calls  are  answered.  With  the  system  in- 
stalled at  St.  John's  the  nurse  cannot  "clear  out"  a  call  without  going 
to  the  room  where  it  originated  and  resetting  the  switch.  This  is  done 
by  pressing  a  handle  back  into  place.  This  feature  assures  that  the 
signal  will  continue  to  be  shown  until  the  call  has  been  answered.  The 
soft  pull  cord  is  more  easily  handled  by  a  sick  man  than  a  spring  push- 
button, and  since  all  electric  wires  end  at  the  wall  plate  he  cannot  be  in- 
jured by  accidental  shock  or  by  rolling  on  to  the  hard  pear-shaped  but- 
ton. A  low-voltage  sign  transformer  furnishes  the  11-volt  energy  for 
the  signal  system,  which  serves  240  private  patients'  rooms  besides  the 


LAMPS  AND  LIGHTING  CIRCUITS 


131 


general  wards.  For  the  latter  individual  lamps  have  been  provided  at 
the  patient's  beds,  so  that  the  source  of  any  call  can  be  followed  back 
promptly.  Some  of  the  larger  wards  are  also  furnished  with  annunciator 
groups.  The  rooms  where  delirious  patients  are  confined  have  emer- 
gency call  buttons  near  the  doors  for  use  of  the  nurses.  These  light  blue 
lamps  at  the  doors  and  in  the  various  signal  centers,  indicating  that  help 
is  urgently  needed  and  summoning  anyone  who  may  be  near.  C.  J. 
Sutter  devised  this  system  which  is  shown  in  Fig.  1. 

Lighting  Fixtures  in  a  Bank. — The  accompanying  Fig.  1  shows  the 
type  of  lighting  fixture  used  in  the  banking  space  on  the  second  floor  of 


4th  Floor 


Lighting 
Fixture 


XhX 


Each  winch  controls  one  outlet 
on  each  side  of  column,  winches 
on  alternate  columns 


Detachable  Cranks 


2nd  Floor 


FIG.    1. — LIGHTING  FIXTURES  IN  A  BANK. 

the  Continental  &  Commercial  Bank  Building,  Chicago.  Supported 
from  the  crests  of  all  of  the  arches  in  each  bay  are  semi-indirect  lighting 
fixtures,  containing  eleven  60- watt  tungsten  lamps,  arranged  so  that  they 
can  be  lowered  for  cleaning  and  relamping.  Each  of  these  fixtures  is  sup- 
ported by  two  bronze  cables  which  run  over  pulleys  concealed  in  the  ceiling 
and  terminate  in  a  hand-operated  winch.  When  the  fixtures  are  lowered 
the  electrical  connection  is  automatically  broken  at  the  ceiling  so  that 


132  HANDBOOK  OF  ELECTRICAL  METHODS 

the  lamp  sockets  can  never  be  energized  when  the  fixture  is  being  cleaned 
or  relamped. 

The  disconnect  device  consists  of  two  plungers  which  form  the 
terminals  of  the  lamp  fixture.  When  the  fixture  is  in  position  to  be 
lighted  the  plungers  are  pressed  by  helical  springs  against  segments 
which  connect  with  the  terminals  of  the  service  lines.  An  interlocking 
device  is  installed  which  prevents  arcing  at  the  disconnecting  point  by 
opening  a  service  switch  when  the  fixture  is  lowered. 

It  may  be  interesting  to  note  that  these  lamps  are  all  fed  from  the 
fourth-floor  cut-out  cabinets,  on  account  of  the  height  of  the  ceiling,  and 
are  controlled  by  momentary-contact  pilot  switches  which  operate 
remote-control  switches  located  in  the  cut-out  cabinets  on  the  fourth 
floor.  The  pilot  switches  are  installed  in  gangs  on  columns  at  four 
corners  of  the  banking  space,  so  that  all  of  the  bank  ceiling  lamps  can  be 
controlled  from  any  one  of  these  positions. 

Control  of  House  Lamps  from  Central  Switch  (By  S.  Fisher). — It  is 
easy  to  arrange  the  wiring  of  a  house  so  that  a  given  number  of  down- 
stairs emergency  lamps  can  be  switched  on  from  an  upstairs  apartment 
in  case  of  a  burglar  "  scare."  While  the  cost  is  a  little  greater  than  for 

Master  Switch  in 
^^    Owner's  Koom 


Off  i      I  On  II 

Two-Way  \  Switches 

A 

)Stair  Qv  Dining  Room  (*)  Living  Room 

FIG.    1. CONTROL  OF  HOUSE  LAMPS  FROM  CENTRAL  SWITCH. 

the  ordinary  way,  this  expense  is  negligible  compared  to  the  satisfaction 
felt  by  the  owner  who,  hearing  a  noise,  can  flood  the  downstairs  rooms 
with  light.  The  two-way  scheme  of  Fig.  1  applies  where  wall  switches  are 
used.  One  position  of  the  switch  is  connected  up  as  the  live  stud,  and 
the  other  contact  is  tied  to  the  master  switch  in  the  owner's  room. 
Closing  this  switch  lights  all  the  other  lamps,  regardless  of  the  position 
of  their  switches,  and  these  lamps  cannot  be  extinguished  except  at  the 
point  where  they  were  turned  on.  If  desirable  several  master  switches 
can  be  employed  on  various  floors,  any  of  which  will  turn  on  all  the  lamps. 
Mercury-vapor-incandescent  Lamp  Cabinet  for  Photographic  Work. 
— After  combating  the  prejudices  which  subjects  display  against  having 


LAMPS  AND  LIGHTING  CIRCUITS 


133 


their  photographs  taken  under  the  greenish  glare  of  the  mercury  vapor 
lamp,  M.  J.  Steffens,  a  Chicago  photographer  whose  work  is  confined  to 
portraiture  of  the  best  class,  has  constructed  a  lamp  cabinet  for  use  in  his 
studio,  in  which  the  red  rays  from  carbon-filament  "linolite"  lamps  are 
combined  with  the  mercury- vapor  light.  As  a  result  of  this  combination 
the  illumination  afforded  is  nearly  natural  in  color,  and  effects  are  said 
to  be  obtained  on  the  photographic  plate  that  have  been  impossible  with 
other  qualities  of  either  artificial  or  natural  light.  The  "snappiness" 
of  outline  of  the  mercury  lamp  is  retained,  while  the  red  rays  render  the 
representation  of  lips  and  skin  tones  more  nearly  correct.  Of  course, 
the  electrical  efficiency  of  the  illumination  is  reduced  from  the  high  figure 
attained  by  the  mercury-vapor  tubes  alone,  as  the  consumption  of  the 
complementary  carbon  lamps  exceeds  that  of  the  tubes  themselves. 


Merc 

Yapo 

1 

L 

L^- 

Car 
Fila 

ii  —  «*  — 

Tncan 
Lai 

& 

FIG.  1. — PHOTOGRAPHER'S  LIGHT  CABINET. 


The  cabinet  (Fig.  1)  constructed  for  use  in  Mr.  Steffens'  studio, 
consists  of  an  oak  frame,  4  ft.  wide  and  7  ft.  high,  in  which  are  mounted 
two  Copper-Hewitt  self-starting  mercury-vapor  lamps  with  tubes  vertical. 
On  the  white-enamel  reflectors  of  these  lamps  and  paralleling  the  tubes 
on  each  side  are  mounted  polished  reflecting  troughs,  each  containing  four 
16-c.p.  carbon-filament  "linolite"  lamps.  Experiments  have  been  made 
with  clear-globe  and  red-dipped  lamps,  and  a  combination  of  the  two  is 
at  present  used  in  the  Steffens  studio.  Each  of  one  the  Cooper-Hewitt 
lamps  consumes  385  watts  at  110  volts,  while  the  eight  16-c.p.  carbon 
lamps  required  to  correct  the  color  characteristic  take  440  watts.  This 
obviously  reduces  the  high  electrical  efficiency  of  the  mercury-vapor 
installation,  but  it  works  important  results  in  the  satisfaction  of  patrons 


134 


HANDBOOK  OF  ELECTRICAL  METHODS 


unaccustomed  to  the  mercury- vapor  light,  and  who  object  to  its  use. 
The  cabinet  containing  the  lamps  is  equipped  with  a  tracing  cloth 
shade  for  securing  diffused  illumination,  and  is  also  fitted  with  three  sets 
of  sliding  curtains,  so  that  the  light  cast  on  the  subject  can  be  controlled 
perfectly  in  amount  or  direction.  The  lamps  are  energized  through  a 
flexible  cable,  with  a  plug  connection,  so  that  the  cabinet  can  be  rolled 
to  any  part  of  the  studio. 

At  a  national  convention  of  photographers  in  Milwaukee  during  1910, 
Mr.  Steffens  was  awarded  first  prize  for  having  produced  the  "most  useful 
and  valuable"  protrait  device  during  the  year. 

Automatic  Extension  of  Connection  Bell  (By  W.  H.  Johnson). — On 
one  occasion  the  writer  made  the  following  use  of  a  two-way  switch 
when  called  in  to  install  a  telephone  extension  bell  in  a  small  factory. 
It  was  desired  to  have  the  extension  bell  ring  out  in  the  shop  when  no 
one  was  in  the  office  to  answer  it,  but  some  means  was  also  required 
for  cutting  off  the  bell  when  the  office  was  occupied.  The  office  was  on 
the  ground  floor  in  a  corner  so  dark  that  artificial  light  was  needed  all 


60600 

FIG.    1. AUTOMATIC  CUT-OUT  FOR  EXTENSION  BELL. 

day.  As  it  seemed  safe  to  assume  that  the  bookkeeper  or  his  assistant 
would  turn  on  the  lamps  while  they  were  in  the  office  and  switch  them  out 
of  circuit  when  they  left,  both  the  lighting  circuit  and  the  bell  circuit 
were  connected  through  the  two-way  switch  Fig.  1.  writh  the  result 
that  when  the  lamps  were  lighted  the  bell  was  out  of  circuit  and  when 
the  lights  were  extinguished  the  bell  was  connected.  Of  course,  the 
lamp  and  bell  circuits  are  entirely  independent  and  insulated  from  each 
other.  The  arrangement  has  proved  an  entire  success  so  far  as  the 
automatic  disconnection  of  the  bell  is  concerned. 

Economical  Street-lighting  Wiring  Arrangement. — The  Worcester 
(Mass.)  Electric  Light  Company  installed  a  number  of  trial  circuits  of 
4-amp.,  75-watt  tungsten  series  incandescent  lamps  early  in  1912  in 
connection  with  the  illumination  of  outlying  districts.  To  economize 
in  the  feeder  investment  for  this  work,  Fred  H,  Smith,  superintendent 


LAMPS  AND  LIGHTING  CIRCUITS 


135 


of  the  company,  devised  a  plan  by  which  energy  for  the  operation  of 
each  circuit  is  derived  from  the  regular  2300-volt,  single-phase  com- 
mercial service  of  the  plant.  Each  circuit  of  incandescent  lamps  con- 
tains from  fifty  to  seventy-five  lamps  looped  through  a  suburban  zone 
from  a  constant-current  transformer  located  in  a  pole  box  in  the  imme- 
diate neighborhood  of  the  lamp  district.  The  constant-current  trans- 
former is  connected  across  the  2300-volt  line,  one  side  being  fused  and 
the  other  side  connected  through  a  solenoid  switch,  the  actuating  coil  of 
which  is  in  series  with  one  of  the  company's  regular  street  arc  circuits 
passing  the  transformer  case. 


E 

2300  V.-A.-C. 
"""  Circuit 

D.-C.  Arc  ' 

Circuit 
—  X  X-^-( 

—  X  X- 

Fuse  -#; 

p.—  *- 

PS                         Inc.Lamp  Circuit 

J 

11                                                                                         \ 

=*  ^°                     O               0                O                O                O               O        O 

—  o                   Constant  Current 

Solenoid  Switch  Transformer 

FIG.    1. ECONOMICAL  STREET-LIGHTING  WIRING  ARRANGEMENT. 

The  incandescent  service  is  thrown  on  automatically  at  the  time  the 
regular  arc  service  is  switched  into  operation.  The  plugging  in  of  the 
arc  lamps  permits  current  to  pass  through  the  solenoid  switch  coil  in 
the  pole  box,  thereby  closing  the  contacts  of  the  local  constant-current 
transformer  primary  and  starting  the  operation  of  the  series  incandescent 
lamps.  In  order  to  keep  the  incandescent  circuit  constantly  in  service 
regardless  of  the  current  fluctuations  and  regulation  of  the  arc  lamp  cir- 
cuit, a  pole  piece  is  installed  in  the  core  of  the  solenoid  switch,  so  that  the 
plunger  is  held  firmly  against  it  as  soon  as  a  starting  current  is  passed 
through  the  arc  circuit  and  coil.  In  the  morning  when  the  arc  circuit 
is  cut  off  the  incandescent  service  remains  on  until  an  operator  at  the 
distributing  substation  utilizes  alternating  current  to  demagnetize  the 
solenoid  core  and  permit  the  plunger  to  drop  and  break  the  incandescent 
circuit.  The  solenoid  switch  is  of  the  oil  type.  Fourteen  incandescent 
circuits  of  this  type  are  now  in  operation  at  Worcester,  the  load  on  each 
varying  from  4  kw.  to  10  kw.  The  effect  upon  the  2300-volt  lines  has 
been  negligible,  and  by  the  use  of  the  automatic  switch,  which  is  built 
for  high-potential  operation,  no  patrolman  is  required  to  handle  the 
incandescent  switching.  The  system,  of  which  a  diagram  is  presented 
in  Fig.  1,  has  saved  money  in  underground  conduits,  ducts  and  feeders, 
besides  eliminating  an  expensive  switchboard  at  the  main  distributing 
center. 

10 


136 


HANDBOOK  OF  ELECTRICAL  METHODS 


All-day  Supervision  of  Arc  Circuits. — When  the  plug  connectors  are 
withdrawn  from  the  switchboard  jacks  controlling  arc-lamp  circuits  in 
the  St.  Louis  substations  test  wires  are  plugged  in  their  place,  each 
pair  lighting  a  couple  of  4-c.p.  lamps  from  the  220-volt  bus  through 
one  of  the  outside  arc-circuit  loops.  The  test  wires  are  formed  up  to 
length  so  that  each  enters  its  individual  jack  and  makes  connection 
with  the  test  lamps  correspondingly  numbered.  These  test  lamps  are 
thus  connected  up  all  day,  as  long  as  the  arc  circuits  are  not  in  use.  If  a 
lamp  goes  out  it  is  the  duty  of  the  station  operator  to  call  up  the  trouble 
department  and  notify  it  of  the  number  of  the  circuit  in  trouble  in  order 
that  repairs  can  be  started  without  delay.  The  operator  is  also  required 
to  look  at  the  test  lamps  once  every  hour,  when  he  reads  his  meter,  mak- 
ing a  note  of  any  circuits  open.  He  must  then  call  the  trouble  depart- 


o 

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Street  Arc 

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1    220V 

Test 


Lamps 


FIG.    1. ALL-DAY  SUPERVISION  OF  ARC  CIRCUITS. 

ment  and  report  whether  or  not  all  test  lamps  are  burning  properly. 
These  calls  must  be  made  hourly  whether  trouble  is  present  or  not. 
This  system  of  all-day  supervision  of  arc  circuits  has  greatly  reduced 
the  number  of  cases  of  trouble  going  undiscovered  until  nightfall.  With 
the  low  voltage  employed  trimmers  cannot  get  a  shock  of  more  than  220 
volts,  or  110  volts  to  ground,  but  they  are  instructed  to  wear  rubber 
gloves  when  handling  arc  lamps  on  the  street.  The  scheme  is  shown 
in  Fig.  1. 

Automatic  Control  of  Curb  Lighting  Fed  from  Edison  System. — The 
business  section  of  Dayton,  Ohio,  is  lighted  by  360  340-watt  tungsten 
clusters,  divided  into  seven  groups,  each  fed  at  a  convenient  point  from 


LAMPS  AND  LIGHTING  CIRCUITS 


137 


the  220-volt  Edison  three-wire  mains  of  the  Dayton  Lighting  Company. 
Formerly  controlled  by  hand  from  street  switches,  this  lighting  is  now  all 
manipulated  practically  simultaneously  from  the  station  switchboard, 
a  magnet- switch  scheme  being  used  which  has  saved  much  of  the  wiring 
required  with  the  usual  distribution  or  pilot-wire  controls.  The  scheme, 
which  is  due  to  0.  H.  Hutchings,  general  superintendent  of  the  company, 
.is  illustrated  in  simplified  form  in  Fig.  1.  Closing  one  of  the  control 
switches  at  the  right  energizes  the  magnet  contactor  of  a  nearby  section. 
As  this  section  lights  up,  it  in  turn  energizes  the  contactor  of  section  No. 
2,  and  the  action  is  repeated  throughout  the  system,  until  the  lighting 
of  the  last  section  is  indicated  by  the  pilot  lamps  on  the  switchboard. 
One  switch  thus  controls  the  four  lower  60-watt  lamps  on  the  posts, 


Midnight         All-night 


Station  220- Volt  Bus 


rO-r£i  Pilot  Lamps 
i       at  Station 

Midnight  <\<i          <\A    All-night 
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Pilot  Wire 

Section  No.2  Contactors 

FIG.    1. AUTOMATIC  CONTROL  OF  CURB  LIGHTING  FED  FROM  EDISON  SYSTEM. 


operated  till  midnight ;  the  other  governs  the  single  100- watt  units  operated 
all  night.  Although  not  shown  in  the  sketch  to  avoid  complication, 
each  group  is  itself  balanced  across  the  three-wire  system,  double-pole 
switches  taking  the  place  of  the  single  contacts  indicated.  Individual  sets 
of  these  100-amp.  General  Electric  carbon -break  contacts  are  mounted, 
with  the  section  fuses  and  meter,  in  the  30-in.  by  34-in.  gasketed  manhole 
box  installed  at  the  feeding  point  of  each  section.  The  meters  are  read 
once  a  month  and  the  switches  are  inspected  and  cleaned  at  this  time. 
Each  magnet  winding  consumes  about  0.3  amp.  at  110  volts  in  its  hold- 
ing position,  and  the  contacts  carry  58  amp.  to  90  amp. 


138 


HANDBOOK  OF  ELECTRICAL  METHODS 


From  the  closing  of  the  control  switch  to  the  flashing  of  the  corre- 
sponding pilot  lamp,  barely  one  second  is  required  for  the  impulse  to 
traverse  the  seven  switches  and  a  total  distance  of  10,500  ft.  Half  of 
this  path  is  in  No.  12  pilot-wire  circuit,  the  average  length  of  pilot  cir- 
cuit being  785  ft.  The  system  cost  $120  per  switch  station  to  install, 
exclusive  of  meters,  and  now  saves  about  one-halt  hour's  daily  opera- 
tion, due  to  irregular  lighting,  or  about  60  kw.-hr.  per  day,  in  addition 
to  labor.  Half  a  mile  from  the  nearest  post -lighting  circuit,  the  Dayton 
company  also  lights  a  bridge  with  alternating-current  multiple  tungsten 
lamps,  the  control  of  which  has  been  effected  by  extending  a  pilot  circuit 
and  magnet  switch  from  the  direct-current  curb  system,  replacing  an 
unsatisfactory  time  switch  formerly  used  at  the  bridge.  The  cost  of 
operating  the  curb  system  is  $55  per  340-watt  post  per  year. 

Remote-Controlled  Operation  of  Peoria's  Ornamental  Lighting. — 
The  240  five-lamp  standards  which  light  the  downtown  section  of  Peoria. 
111.,  are  fed  in  groups  of  six  to  the  curb  block  from  the  110/220-volt 


Control  Wire 


Messenger 
Call  Box 


o  o 

Q     Lamps 

O    O  , 

60-CycIe,  Three- Wire 


FIG.    1. REMOTE-CONTROLLED  OPERATION  OF  PEORIA  S  ORNAMENTAL  LIGHTING. 


alternating-current  three-wire  mains  and  are  turned  on  and  off  by  means 
of  a  remote-control  pilot  circuit  which  operates  relay  switches  at  the 
feeding  points.  By  an  ingenious  arrangement  a  step-by-step  mechanism 
permits  the  four  60- watt  lamps  or  the  single  100- watt  units  to  be  turned 
positively  on  and  off,  independently  of  the  others,  although  only  a  single 
control  wire  is  used. 

At  each  feeding  point  for  a  six-post  block  a  relay  switch  is  installed 
in  a  post  base.  It  includes  a  1000-ohm  telephone  relay,  bridged  between 
the  control  wire  and  the  system  neutral,  and  the  50-ohm  switch  magnet, 
whose  winding  is  energized  through  the  relay  contact.  This  operating 
magnet  works  against  the  switch  shaft,  rotating  it  90  deg.  each  time  the 


LAMPS  AND  LIGHTING  CIRCUITS  139 

magnet  is  energized.  Pitman  rods  from  this  shaft  control  contacts 
dipping  into  the  two  mercury  cups,  one  for  the  top-lamp  circuit  and  the 
other  for  the  lower  lamps.  The  crank  pins  for  these  rods  are  also  quartered 
90  deg.,  as  the  sketch  shows,  so  that  in  succession  both  contacts  may  be 
down,  or  one  up  and  one  down,  or  both  up.  This  series  of  positions  is 
passed  in  the  course  of  one  rotation,  lighting  first  the  lower  lamps,  then 
the  top  lamps,  then  extinguishing  the  lower  lamps  and  finally  extinguish- 
ing the  top  lamps. 

Some  difficulty  was  at  first  experienced  in  timing  the  impulses  to 
operate  all  the  relays  and  switches  positively,  but  the  messenger  call- 
box  mechanism  finally  adopted  solved  this  problem,  the  impulses  now 
being  fixed  at  about  fifteen  seconds'  duration  with  five-second  intervals. 
Another  slight  source  of  trouble  has  been  the  sensitiveness  of  the  relays 
as  first  installed.  A  heavy  blow  to  the  switch  post,  such  as  a  wagon 
riding  over  the  curb,  would  cause  a  momentary  closure  of  the  contact, 
putting  the  corresponding  circuit  out  of  step.  But  these  minor  difficulties 
have  been  speedily  cleared  out,  and  each  switch  before  being  installed 
received  a  test  of  500  operations  without  a  single  failure.  The  switch 
mechanism  is  inclosed  in  a  6-in.  by  10-in.  iron  box,  2  in.  deep,  with  fiber 
entry  bushings  for  the  wires.  The  outfits  cost  about  $12  each  as  made 
in  a  local  shop.  The  No.  10  control  wire  which  operates  the  forty  switches 
has  a  total  length  of  about  3  miles.  Each  relay  takes  about  0.1  amp. 
and  the  operating  magnets  2  amp.  momentarily.  C.  A.  Rich,  foreman  of 
the  underground  department  for  the  Peoria  Gas  &  Electric  Company, 
devised  the  installation  described. 

Electric  Lighting  from  Three-phase  Circuits  (By  G.  P.  HOXIE).— 
It  is  prevalent  practice  to  distribute  electrical  energy  in  industrial  plants 
by  means  of  the  three-phase  system,  principally  because  of  the  simplicity 
and  reliability  of  the  induction  motor.  Although  other  voltages  are 
used,  220  and  440  are  the  most  common.  Usually  the  proportion  of  the 
total  energy  generated  required  for  lighting  is  small.  Most  of  it  is 
utilized  for  motor  circuits  and  its  adaptability  for  electric  lighting  is  of 
secondary  importance.  Practically  all  lighting  equipment  operates 
only  from  single-phase  circuits;  but  as  a  rule  it  is  not  advisable  in  industrial 
plants  to  generate  single-phase  current  solely  for  lighting  service.  So 
some  plan  must  be  adopted  whereby  single-phase  circuits  for  the  operation 
of  lighting  equipment  can  be  arranged  from  three-phase  circuits. 

One  of  the  simplest  schemes  for  lighting  from  a  three-phase  circuit 
is  suggested  in  Fig.  1.  Single-phase  branches  are  tapped  from  the 
three-phase  main  and  the  voltage  across  each  branch  will  be  the  same  as 
that  between  any  two  wires  of  the  main.  In  arranging  circuits  after  the 
manner  shown,  the  loads  on  the  branch  circuits  should  be  so  divided  that 
each  of  the  three  phases  will  be  about  equally  loaded.  That  is,  phases 


140 


HANDBOOK  OF  ELECTRICAL  METHODS 


A,  B  and  C  (Fig.  1)  should  each  serve  groups  of  lighting  appliances  of 
approximately  equal  inputs.  Fusible  cut-outs  should  be  inserted  in  each 
branch  circuit  where  it  branches  from  the  mains. 

In  Fig.  1  the  mains  have  a  potential  of  220  volts,  therefore  220- volt 
incandescent  and  arc  lamps  can  be  fed  from  the  branches.  With  440- 
volt,  three-phase  mains  it  is  not  usual  to  connect  single-phase  lighting 
circuits  direct  to  the  mains.  Some  type  of  transforming  device  is  inter- 
posed between  the  mains*  and  the  branch  lighting  circuits,  as  will  be 
hereinafter  described. 

Carbon-filament  incandescent  lamps  for  220  volts  cost  more  than  do 
similar  lamps  for  110  volts  and  they  have  shorter  lives  and  are  less 
efficient  than  are  110- volt  lamps.  Consequently  in  some  installations, 
where  three-phase  energy  is  distributed  at  220  volts,  110-volt  carbon 

Three-phase  Mains 


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2iM 

! 

2;n 

. 

FIG.    1. MULTIPLE  SINGLE-PHASE  CIRCUITS  FROM  THREE-PHASE  CIRCUITS. 

incandescent  lamps  are  operated  two  in  series  as  indicated  in  Fig.  2. 
In  these  installations  multiple  arc  lamps  are  used  that  are  built  for  opera- 
tion on  220  volts.  Metallic-filament  lamps  for  110  volts  are  cheaper, 
more  efficient  and  have  longer  lives  than  similar  ones  for  220  volts  and 
have  more  rugged  filaments,  hence  are  less  liable  to  breakage.  For 
these  reasons  metallic-filament  lamps  are  sometimes  connected  as  out- 
lined in  Fig.  2.  When  ordering  metallic-filament  incandescent  lamps 
that  are  to  be  operated  two  in  series  it  should  be  specified  in  the  order 
that  the  lamps  are  for  series  operation  so  that  they  can  be  especially 
selected  for  this  service.  Metallic-filament  lamps  are  designated  by 
their  nominal  inputs  in  watts  and  two  lamps  of  the  same  nominal  input 
may  vary  considerably  in  actual  input.  If  two  such  lamps,  having 
different  inputs,  are  connected  in  series  across  a  circuit  of  twice  their 
nominal  voltage,  one  of  the  lamps  may  be  considerably  overloaded  and 
will  have  a  correspondingly  shorter  life. 


LAMPS  AND  LIGHTING  CIRCUITS 


141 


Two  plans  for  wiring  buildings  for  motors  and  lamps  using  three- 
phase  sub-mains  are  shown  at  A  and  B,  Fig.  3.  The  lighting  panel  box 
used  is  shown  in  Fig.  4.  Both  of  the  buildings  are  served  from  the  three- 
phase  main  in  the  street  in  front  of  them.  In  the  plan  A  energy  for  both 
lamps  and  motors  is  taken  from  the  same  sub-main  which  traverses  the 

Three-phase  Mains 


FIG.    2. SERIES-MULTIPLE  SINGLE-PHASE  CIRCUITS  FROM  THREE-PHASE 

CIRCUITS. 


Three-phase  Main 


FIG.    3. WIRING  FROM  THREE-PHASE  MAINS. 

center  of  the  building,  while  at  B  individual  sub-mains  are  arranged  for 
lamps  and  for  motors.  Where  it  is  essential  that  the  wiring  be  installed 
economically  and  the  motors  served  are  of  small  size  the  plan  indicated 
at  A  can  be  used;  but  where  a  first-class  installation  is  desired  it  is  better 
to  divide  the  lamp  and  motor  sub-mains  as  suggested  at  B.  The  disad- 


142 


HANDBOOK  OF  ELECTRICAL  METHODS 


vantages  of  plan  A  are  (1)  that  the  heavy  momentary  currents,  drawn  by 
the  motors  at  times  of  starting  or  of  changes  in  load,  may  cause  poor  vol- 
tage regulation  and  the  consequent  unsteadiness  of  light,  and  (2)  that 
trouble  on  the  motor  circuits  may  melt  the  main  fuse  and  extinguish  all 
of  the  lights.  It  is  assumed  for  plans  A  and  B  that  the  voltage  regulation 
on  the  main  in  the  street  is  good.  With  plan  B  conditions  on  the  motor 
circuits  cannot  to  any  extent  affect  the  regulation  on  the  lighting  sub- 
main,  as  it  is  independent  and  the  fuses  protecting  the  motor  sub-main 
can  melt  without  extinguishing  the  lights,  because  only  energy  for  motors 
feeds  through  them. 


Panel  Box 


Sub-Main 


FIG.    4. THREE-PHASE  TO  SINGLE-PHASE  PANEL  BOX  FOR  LIGHTING  SYSTEM. 

In  Fig.  4  is  delineated  a  method  of  arranging  a  panel  box  that  might 
be  used  in  plan  A  or  B,  Fig.  3.  Three  conductors  are  " tapped"  to  the 
three-phase  sub-main  and  carried,  through  fuses,  to  the  three  busbars 
of  the  panel  box.  In  the  panel  box  the  single-phase  branch  circuits  are 
connected  successively  across  each  of  the  phases,  in  rotation,  so  that  the 
lighting  load  will  tend  automatically  to  balance  itself.  Edison  plug 
cut-outs  are  interposed  between  the  busbars  and  the  terminals  of  the 
single-phase  branch  circuits.  The  scheme  of  connections  indicated  in 
the  panel  box  of  Fig.  4  is  merely  an  elaboration  of  that  suggested  in  Figs. 
1  and  2.  In  Fig.  4,  if  the  sub-mains  operated  at  220  volts,  220-volt 
incandescent  lamps  would  be  used,  or  110-volt  lamps  might  be  used  in 


LAMPS  AND  LIGHTING  CIRCUITS 


143 


groups  of  two  in  series  like  the  arrangement  of  Fig.  2.  If  the  sub-main 
pressure  was  110  volts,  110-volt  lamps  would  be  used  on  the  branch  cir- 
cuits. If  the  voltage  on  the  sub-main  was  440,  some  other  method  would 
be  utilized  as  hereinafter  outlined. 

A  three-phase  distribution  system  for  an  industrial  plant  is  indicated 
in  Fig.  5.  An  individual  three-phase  feeder  is  carried  from  the  generat- 
ing station  to  each  of  the  buildings  on  the  property.  Just  within  each 
of  the  three  larger  buildings,  Shops  I,  II  and  III,  the  feeder,  after  passing 
through  a  service  switch  and  fuses,  is  divided  and  carried  into  a  distribu- 
tion box  for  motor  circuits  and  into  one  for  lamp  circuits.  The  store- 


k 

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| 



:  ;  a 

--  'S 
:  :  £3 

::  W 

Store 
:     House  [— 

p 

SLop 

SLc 

P 

Shop 

::  W 

-• 

I 

I] 

III 

::      < 

lenerating 
Station. 

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iDist. 
|Box 

Lamp 

Dist. 
IBox 

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Feeder 
Box\ 

w/M  |  |_l 

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\IL.r.ee-phase 

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ders 

FIG.    5. A  THREE-PHASE  DISTRIBUTION  SYSTEM. 

house  is  served  by  a  small  feeder  terminating  in  a  lighting  distribution 
box.  If  the  buildings  have  but  one  story,  motor  branch  circuits  might 
feed  direct  from  the  distribution  boxes,  or  mains  might  be  carried  from 
them  the  length  of  the  buildings  and  motor  branch  circuits  would  be  con- 
nected to  the  main  as  outlined  at  B,  Fig.  3.  Lighting  circuits,  if  the 
buildings  of  Fig.  5  were  all  of  one  story,  might  be  arranged  as  detailed  in 
Fig.  3,  B,  and  Fig.  4.  If  the  buildings  were  of  more  than  one  story,  the 
plan  of  Fig.  6  could  be  adopted.  In  this  diagram  fuses  and  switches  are 
not  indicated.  From  the  feeder  box  mains  are  carried  to  the  distribu- 
tion boxes,  for  motor  and  for  lamp  circuits,  which  are  located  in  the 
basement.  From  the  distribution  boxes  risers  are  carried  through  the 
floors  above  and  panel  boxes  are  located  on  each  floor.  Only  one  set  of 
risers  and  panel  boxes  is  indicated  in  Fig.  6,  but  with  a  building  covering 
a  large  area  several  sets,  duplicates  of  those  shown,  might  be  necessary. 
The  distribution  boxes  in  the  basement  would,  in  such  a  case,  be  so 
arranged  that  all  of  the  risers — which  would  be  mains — would  feed  from 


144 


HANDBOOK  OF  ELECTRICAL  METHODS 


them.  It  might  be  desirable  in  some  instances  to  carry  individual  mains 
from  one  of  the  distribution  boxes  to  each  of  the  panel  boxes  or  to  a 
group  of  two  or  three  panel  boxes.  This  plan  would  probably  be  fol- 
lowed, particularly  with  the  electric-light  circuits,  if  a  building  of  six 


;%^%££2^^^^ 
FIG.    6. PLAN  OF  WIRING  FOR  BUILDING  OF  SEVERAL  STORIES. 


Load 


-110  V.- 


Inductive  Winding 

220  V^ — ' 

Line 


no  v,  4103, 


<--220V-7-» 


-440V. 

Line 


3-Wire  Lighting  Circuits 
«_220  -V- > 


Balancing 
Coil 


<220  V.,  ,220  V-*. 
*— 220  V^ > 


Three-Phase 
Supply- Circuit  Line 


FIGS.    7,    9    AND     10. DIAGRAMS    OF    THREE-PHASE     AUTO-TRANSFORMER,     THREE-WIRE, 

440-VOLT    AUTO-TRANSFORMER     AND     THREE-WIRE     SYSTEMS    BAL- 
ANCED   ON    A   THREE-PHASE    SYSTEM. 

stories  or  over  were  being  wired.  The  reason  for  this  is  that  circuits 
can  be  designed  to  provide  closer  voltage  regulation  if  small  groups  of 
boxes — rather  than  large  groups — located  reasonably  close  together  are 
each  fed  with  an  individual  main. 


LAMPS  AND  LIGHTING  CIRCUITS  145 

Because  they  are  very  economical  of  copper  and  permit  the  use  of 
individually  fed  110- volt  incandescent  lamps  (instead  of  two  110-volt 
lamps  in  series)  110-220- volt  three-wire  circuits  are  very  extensively 
used  for  distributing  electrical  energy  for  interior  lighting.  Three-wire- 
110-220-volt  alternating-current  circuits  can  be  obtained  from  220-volt, 
single-phase,  alternating-current  circuits  with  an  auto-transformer  as 
shown  in  Fig.  7.  How  this  principle  is  applied  to  three-phase  circuits 
will  be  shown  later.  Auto-transformers  for  this  and  similar  services  are 
regularly  manufactured  and  are  usually  arranged  in  standard  transformer 
cases  as  suggested  in  Fig.  8.  The  load  on  such  an  auto-transformer  is 


Weatherproof 
Iron  Case 


FIG.    8. AUTO-TRANSFORMER. 

equal  to  the  difference  in  the  loads  on  the  two  sides  of  the  three-wire 
system  and  the  size  of  the  auto-transformer  to  be  used  can  be  determined 
accordingly.  For  example :  If  the  load  on  one  side  of  a  three-wire  system, 
like  that  of  Fig.  7,  were  100  amp.  and  the  load  on  the  other  side  were 
150  amp.  the  auto-transformer  would  be  loaded  with  but  150  —  100  =  50 
amp.  The  amount  of  unbalance  that  should  be  provided  for  in  each 
case — hence  the  size  of  the  auto-transformer — is  determined  by  local 
conditions.  If  there  is  probability  of  great  unbalance  and  if  the  lamps 
must  be  kept  burning  at  any  reasonable  cost,  it  should  be  assumed  that 
one  side  of  the  three-wire  system  may  be  fully  loaded  while  there  is  no 
load  on  the  other  side.  This  would  mean  that  the  auto-transformer 
should  have  a  rating  equal  to  the  entire  load  on  one  side  of  the  three- wire 
system.  However,  in  practice  the  amount  of  unbalance  does  not,  where 
branch  circuits  are  carefully  laid  out;  often  exceed  10  per  cent,  of  the  total 
load.  On  this  basis  the  rating  of  an  auto-transformer  should  be  10  per 
cent,  of  the  total  load  to  be  connected  to  it.  In  some  installations  the 
amount  of  unbalance  on  a  three-wire  system  is  very  small,  not  exceeding 
5  per  cent,  at  any  time.  But  in  other  cases  the  unbalance  may  be  as  high 
as  15  per  cent,  or  even  30  per  cent.  A  10  per  cent,  unbalance  is  probably 
a  fair  average  working  amount. 

If  an  auto-transformer  is  selected  on  the  basis  of  slight  unbalance,  say 
10  per  cent,   and    the    unbalance  becomes  excessive,   not  very  much 


146  HANDBOOK  OF  ELECTRICAL  METHODS 

can  happen  if  all  circuits  are  properly  protected  by  fuses.  Voltage  above 
normal  may  for  a  time  be  impressed  on  the  lamps  on  one  side  of  the  three- 
wire  system  if  a  fuse  is  melted  by  overload,  or  currents  may  flow  that  are 
great  enough  to  melt  fuses,  extinguishing  or  dimming  the  lights.  But 
these  difficulties  reveal  themselves,  are  readily  corrected  and  ordinarily 
do  no  serious  harm. 

Inasmuch  as  auto-transformers  can  be  purchased  that  are  mounted 
within  weatherproof  cast-iron  cases  they  can  be  arranged  on  the  outside 
walls  of  buildings  or  on  poles.  Apparently  there  are  no  specific  rules 
governing  the  installation  of  large  auto-transformers,  or  balance-coils 
as  they  are  sometimes  called  in  the  National  Electrical  Code.  For  this 
reason  it  would  probably  be  best  to  confer  with  the  local  inspection  bureau 
before  making  an  installation  to  find  just  what  the  district  representative 
would  require.  It  is  probable  that  the  rules  that  govern  the  installation 
of  transformers  would  also  govern  the  installation  of  auto-transformers. 
That  is,  they  must  not  be  placed  inside  of  buildings,  except  stations  and 
substations,  without  special  permission,  and  when  they  are  placed  inside 
of  buildings  certain  precautions  must  be  taken  to  prevent  the  spread  of 
fire  in  the  event  of  the  oil  in  the  cast-iron  case  becoming  ignited.  A 
fireproof  inclosure  of  some  sort,  well  ventilated  to  carry  away  oil 
fumes,  would  probably  be  required  in  buildings  other  than  stations  and 
substations. 

Three-wire  circuits  are,  with  auto-transformers,  obtained  from  220- 
volt,  three-phase  circuits  by  connecting  an  auto-transformer,  like  that  of 
Fig.  7,  across  any  one  or  across  each  of  two  or  of  the  three  phases.  In  Fig. 
10  a  diagram  is  shown  of  three  auto-transformers,  each  serving  a  three- 
wire  circuit  and  each  connected  across  one  of  the  three  phases.  Three- 
wire  110— 220-volt  circuits  can  be  obtained  from  any  one  of  the  phases 
of  a  440-volt,  three-phase  system  by  using  an  auto-transformer  such  as 
that  indicated  diagrammatically  in  Fig.  9.  Equipment  for  this  service 
can  be  purchased  from  any  of  the  principal  builders  of  transformers. 

Transformers  can,  of  course,  be  used  for  any  application  shown  herein 
for  auto-transformers.  But,  as  a  rule,  transformers  for  a  given  applica- 
tion will  be  more  expensive  than  auto-transformers.  This  is  because  a 
transformer  has  two  windings,  a  primary  and  a  secondary,  and  because 
a  transformer  must  always  have  a  rating  equal  to  the  full  load  on  the 
three-wire  system.  It  should  be  noted  that  an  auto-transformer,  ar- 
ranged between  a  single-phase  and  a  three-wire  system,  must  have  suffi- 
cient rating  to  accommodate  the  full  load  current  in  the  line  wires  of  the 
single-phase  system  unless  the  voltage  across  the  outside  wires  of  the 
three-wire  system  is  impressed  on  the  auto-transformer.  For  example, 
an  auto-transformer  operating  as  indicated  in  Fig.  7  need  not  necessarily 
be  of  sufficient  size,  to  accommodate  the  primary  current  in  the  220-volt 


LAMPS  AND  LIGHTING  CIRCUITS 


147 


line,  while  the  auto-transformer  suggested  in  Fig.  9  must  be  of  a  rating 
to  accommodate  the  primary  current  in  a  440-volt  line.  Transformers 
possess  one  advantage  over  auto- transformers.  With  auto-transformers 
the  secondary  circuits  are  electrically  connected  to  the  primary  circuit 
and  a  ground  on  the  secondary  circuit  may  have  the  same  effect  as  one 
on  the  primary  circuit.  Furthermore  the  secondary  circuits  are  at  pri- 
mary potential  above  ground  and  may  give  a  severe  shock  to  a  person 
coming  in  contact  with  them  if  there  is  a  ground  on  the  primary  circuit — 
and  there  usually  is.  With  the  transformer  there  is  no  electrical  connec- 
tion between  primary  and  secondary  circuits,  so  neither  of  the  above 
objections  holds. 

When  auto-transformers  are  used  on  three-phase  circuits  to  feed  three- 
wire  systems  they  should  be  connected  on  the  three  phases  as  outlined 


FIG.    11. AUTO-TRANSFORMER  FOR  LIGHTING  OF  FACTORY  BUILDING. 


in  Fig.  10.  The  three-wire  mains  and  the  branch  circuits  for  lighting 
should  be  so  loaded  that  each  phase  will  be  almost  equally  loaded.  Some 
unbalancing  will  not  appreciably  affect  the  operation  of  the  three-phase 
system.  Just  the  amount  of  unbalancing  that  would  be  permissible  is 
determined  by  the  characteristics  of  the  three-phase  generator,  the  load 
on  it,  and  by  the  character  of  the  equipment  connected  to  the  three- 
phase  circuits.  It  is  probable  that,  with  the  average  generator,  there 


148 


HANDBOOK  OF  ELECTRICAL  METHODS 


can  be,  when  it  is  operating  at  about  full  load,  a  load  unbalance  of  pos- 
sibly 25  per  cent,  between  the  most  lightly  and  the  most  heavily  loaded 
phases  without  the  voltage  regulation  being  affected  enough  to  make 
trouble. 

Suggested  in  Fig.  11  is  an  arrangement  of  equipment  in  an  industrial 
building  whereby  three-wire,  110-220-volt  lighting  circuits  are  fed 
through  an  auto-transformer  from  a  three-phase  feeder.  On  entering 
the  building  from  the  subway,  the  three-phase  feeder  enters  a  feeder 
box  where  mains  are  branched  from  it.  One  phase  only,  for  lighting, 
continues  to  the  auto-transformer,  and  the  other  three-phase  branch 


Generating 
Station 


Building  A 
Lighting  Dist-Box 

Motor  Dist-Box 


Ihree  Wire 
Lighting  Feeder 

_  Three-Phase 
Motor  Feeder 


FIG.    12. LIGHTING  AND  MOTOR  FEEDER  LAYOUT. 

for  motor  circuits  is  carried  into  the  three-phase  distribution  box.  From 
this  box  mains  are  carried  to  panel  boxes  located  about  the  building. 
From  the  auto-transformer  the  three-wire  main  enters  the  three-wire 
lighting  distribution  box.  From  this  box  three-wire  mains  are  run  to 
lighting  panel  boxes  situated  in  the  various  departments  in  the  structure. 
From  the  panel  boxes  single-phase  branches  are  brought  out  and  to  these 
branches  the  electric  lamps  are  tapped.  The  method  of  Fig.  11  resembles 
somewhat  the  scheme  indicated  in  each  of  the  buildings  of  Fig.  5.  The 
difference  is  that  in  Fig.  5  the  lighting  mains  are  three-phase  while  in 
Fig.  11  they  are  three-wire. 

A  single  auto-transformer,  like  that  in  Fig.  11,  on  one  phase  of  a 
three-phase  system  might  unbalance  the  system  excessively,  but  this 
can  be  avoided  by  installing  auto-transformers  in  other  buildings  on  the 
other  phases.  The  connections  for  the  auto-transformer  in  Fig.  11  are 
shown  in  Fig.  9. 


LAMPS  AND  LIGHTING  CIRCUITS 


149 


It  is,  as  hereinbefore  outlined,  often  desirable  to  install  individual 
feeders  for  lamps  and  for  motors.  This  applies  whether  auto-trans- 
formers are  used  or  not.  In  Fig.  12  is  shown  the  feeder  layout  for  a 
manufacturing  plant  generating  220-volt,  three-phase  energy  and  using 


lotor  Panel- 


3-Phase  Busbars 


—  Lamp  Panel 


>l 


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22^  v-        22(£Y. 

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J 

Switches  1 

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Balant 

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Coils 

Three- 

I'hii 

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C 

J 

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Feeders 

Building         Building       Building 

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Threo-Wiro 

Building 

A 


Lighting 

Building 

B 


Feeder 
Building 
C 


FIG.    13. THREE-WIRE  THREE-PHASE  CIRCUIT  FOR  MOTORS  AND  LAMPS. 

separate  feeders  for  motor  and  for  lamp  circuits.  The  pressure  on  the 
three-phase  motor  feeders  is  220  volts  and  that  on  the  lighting  three- 
wire  feeders  is  110-220  volts.  Auto-transformers  connected  as  shown 


i 


440  V.,  3-Ph.  Main 


Entrance 
Box 


3-Ph.Motor 


O 
3-Ph.  Motor 


O 


1 


FIG.    14. LIGHTING  CIRCUITS  FED  THROUGH  TRANSFORMERS. 

in  the  feeder  diagram,  Fig.  13,  are  utilized  to  obtain  three-wire  circuits 
from  the  three  phases.  The  notation  on  this  diagram  corresponds 
with  that  on  Fig.  12  and  indicates  how  the  motor  and  the  lamp  feeders 
are  apportioned. 


150 


HANDBOOK  OF  ELECTRICAL  METHODS 


In  at  least  one  factory  the  method  of  lighting  from  three-phase 
circuits  shown  in  Fig.  14  has  been  used.  The  three-phase  mains  operate 
at  440  volts  and  at  each  lighting  panel  box  a  transformer  is  installed 
which  reduces  the  pressure  to  110  volts  for  the  lighting  circuits.  Three- 
phase  busbars,  fed  by  the  transformer  secondaries,  are  arranged  in  each 
box  and  from  these  buses  single-phase  branches  are  tapped.  The  con- 
nections within  the  lighting  panel  boxes  are  substantially  the  same  as 
those  indicated  in  Fig.  4.  Three-phase  motors  operate  from  the  same 
mains  that  supply  the  lighting  energy. 

Low-frequency  Flicker  Cured  By  Two -phase  Wiring. — In  a  large 
manufacturing  establishment  near  Pittsburgh  the  shop  offices  are 
lighted  from  the  25-cycle  plant  lines.  At  this  low  frequency  the  40 
watt  tungsten  lamps  used  gave  considerable  annoyance  from  flickering. 
The  units  were  hung  low,  and  at  the  high  intensities  on  the  working 


O                                         O             P^se  1            O 

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Phase  1 


O 


O 


O 


Phase  2 


O 


FIG.    1. LOW-FREQUENCY  FLICKER  CURED  BY  TWO-PHASE  WIRING. 

surfaces  this  flicker  became  very  objectionable.  The  trouble  was 
practically  cured,  by  connecting  half  of  the  twenty  lamps  to  the  second 
phase  of  the  two-phase  supply  system.  The  individual  flicker  of  each 
group  is  thus  neutralized  by  the  coincident  "peak"  of  the  other  lamps, 
and  the  total  illumination  on  any  lighted  surface  is  practically  uniform. 
On  examination,  of  course,  the  flicker  of  the  individual  lamps  can  still 
be  detected.  The  second  phase  was,  in  the  case  cited,  easily  accessible, 
and  the  division  of  the  load,  besides  curing  the  flicker,  has  resulted  in  a 
better  balance.  The  method  is  shown  in  Fig.  1. 

Testing  Lamps  by  a  Motor-driven  Machine. — The  home-made  lamp- 
testing  machine  used  by  the  Edison  Electric  Illuminating  Company  of 
Boston,  Mass.,  has  the  special  advantages  of  increased  speed  with  which 
lamps  can  be  tested,  as  compared  with  former  hand  methods,  and  the  use 
of  an  automatic  counter  which  insures  accurate  enumeration  of  all  lamps 
passed  through  the  apparatus.  The  device  consists  of  an  endless  belt 
carrying  about  two  dozen  sockets  spaced  at  6-in.  distances,  three  driving 


LAMPS  AND  LIGHTING  CIRCUITS 


151 


pulleys  and  a  small  110-volt  motor.  Two  brass  contact  strips  3/4  in. 
wide  are  provided  for  a  distance  of  about  2  ft.  below  the  upper  belt  at 
the  left-hand  end  of  the  machine.  Lamps  returned  from  customers' 
installations  are  placed  in  the  sockets,  and  as  the  machine  operates  they 
pass  rapidly  from  right  to  left,  each  base  actuating  the  counter  and  being 
made  alive  as  the  upper  portion  of  the  belt  passes  over  the  brass  contact 
strips.  The  belt  is  3  in.  in  width  and  runs  over  the  contact  strips  just 
long  enough  to  enable  an  operator  at  the  left  of  the  machine  to  see 
whether  each  lamp  burns  properly  or  not. 

Lamps  which  burn  properly  on  this  test  are  culled  from  the  rest  and, 
after  being  photometered  into  two  grades,  are  installed  in  various  company 
buildings,  in  portions  of  its  power  plants  and  substations,  or  sent  to  con- 
tractors for  the  rough  usage  of  field  work.  The  usual  capacity  of  the 
machine  is  about  3000  lamps  per  day,  with  one  man  working  at  each  end 
but  it  has  a  maximum  of  seventy  lamps  a  minute. 

Wiring  for  Extension  Lamp  in  6oo-volt  Series  Circuit. — The  plans  for 
the  wiring  of  a  new  railway  substation  called  for  extension  outlets  so 
arranged"  that  five  lamps  would  be  in  series  across  600  volts,  the  fifth 


FIG.    1. WIRING    FOR    EXTENSION    LAMP    IN    600-VOLT    SERIES    CIRCUIT. 

lamp  being  the  portable  extension  outlet  and  the  other  four  being  sta- 
tionary. The  arrangement  finally  adopted  was,  therefore,  to  shunt 
duplicate  outlets  in  parallel  with  the  portable  outlet  of  the  regular 
series  circuit.  To  operate  an  extension  lamp  at  any  point  it  is  thus  only 
necessary  to  plug  into  the  desired  receptacle,  at  the  same  time  backing 
out  or  switching  off  the  other  lamp  in  multiple.  The  diagram  of 
connections  appears  in  Fig.  1. 

Inexpensive  Lamp  Guard  for  Interurban  Cars. — Following  the  in- 
stallation of  tungsten  lamps  on  its  interurban  cars  operating  between 
Fort  Wayne,  Ind.,  and  Lima,  Ohio,  the  Ohio  Electric  Company  discovered 
that  a  large  percentage  of  lamp  breakage  was  due  to  the  careless  passen- 
ger who  tossed  his  suitcase,  grip  or  parcel  into  the  parcel  rack  without 
noticing  the  tungsten  lamp  above  the  rack.  A  number  of  small  steel 
rods  3/16  in.  in  diameter  were  therefore  bent  as  shown  in  the  drawing, 


152 


HANDBOOK  OF  ELECTRICAL  METHODS 


Fig.  1;  and  flattened  at  each  end  to  receive  holes  for  the  wood  screws 
which  hold  them  in  place.  These  rods,  when  fastened  to  the  woodwork 
of  the  car  above  the  advertising  space,  protect  the  lamps  and  are  said 
to  have  reduced  the  breakage  from  the  above  cause  without  in  any  way 
impairing  the  efficiency  of  the  illumination  or  obstructing  speedy  lamp 
renewals.  The  cost  of  the  guards  was  found  to  be  slight  in  comparison 
with  former  lamp  bills. 

Types  and  Uses  of  Semi -indirect  Lighting  Units  (By  Leonard  V. 
James). — The  tendency  in  modern  lighting  installations  is  undoubtedly 
toward  diffused  illumination,  together  with  an  effort  to  add  to  the  appear- 
ance of  the  room  by  the  use  of  proper  fixtures.  Direct  lighting  from  un- 


Scre 


-Ventilator 


Guard,  */w  Steel 

Flattened  at  Ends  for 

Screw  Holes 


Parcel  Hack 


Car  Window 


FIG.    1. LAMP  GUARD  FOR  INTERURBAN  CARS. 

shaded  sources  and  indirect  lighting  with  all  of  the  light-flux  reflected  to 
the  working  plane  from  a  diffusing  surface  are  the  extremes.  Approach- 
ing the  direct  lighting  there  is  the  type  of  unit  in  which  the  light  source 
is  shielded  by  shades  ranging  from  nearly  clear  glassware  to  translucent 
bowls  and  finally  to  opaque  mirrored  reflectors,  all  of  these  having  a 
more  or  less  directive  effect.  The  so-called  semi-indirect  system  is  really 
a  special  case  of  the  modified  direct,  since  the  most  of  the  useful  light- 
flux  passes  through  the  translucent  bowl. 

The  combination  of  the  direct  and  indirect  lighting  furnished  by  the 
luminous-bowl  units  is  effective  and  pleasing  and  meets  the  public  de- 
mand for  indirect  lighting  together  with  an  apparent  light  source.  In 
a  paper  read  before  the  Illuminating  Engineering  Society  in  June,  1912, 


LAMPS  AND  LIGHTING  CIRCUITS 


153 


Thomas  W.  Rolph  discusses  the  results  of  a  series  of  tests,  suggesting 
that  the  illumination  of  the  ceiling  with  indirect  lighting  is  from  10  to 
15  per  cent,  as  intense  as  that  of  a  direct-lighting  fixture  producing  the 
same  effect  in  the  room.  These  results  seem  to  have  been  verified  by 
the  manufacturers  of  the  luminous-bowl  fixtures  under  discussion,  as 
the  light-flux  used  in  securing  the  desired  effect  appears  in  all  cases  to  be 
almost  exactly  10  per  cent. 


Composition 
or  Metal  Iron 


Opal 
Diffuser 


FIGS.    1  AND  2. LAMPS  AND  REFLECTORS  IN  VERTICAL  POSITION. 

There  are  two  arrangements  of  the  interior  equipment  used  in  the 
fixtures  in  question.  As  a  rule  the  reflectors  and  lamps  are  in  a  vertical 
position,  as  shown  in  Figs.  1,  2  and  3.  The  reflectors  used  are  one-piece 


Reflector 


Metal  01  Composition 


Reflector  °,utlet 

'Reflector  Holder!    [      Composition 
Metal 


Opal 
DiUuser 

Metal 
Receptacle 


Ornamental 

Metal  /  l>  Glass  Bowl 

Glass  Panel  Receptacle          IQW  Vo]tage  Lamp 

to  Illuminate  Bowl 


Outlet  Body 

FIGS.    3  AND  4. LAMPS  AND  REFLECTORS  IN  VERTICAL  AND  HORIZONTAL 

POSITIONS. 

silvered-glass  opaque  reflectors.  The  light-flux  which  illuminates  the 
outside  bowl  passes  through  and  is  directed  by  an  opal  diffuser,  located 
so  that  it  interferes  but  little  with  the  normal  reflection  required  for 
general  illumination.  Fig.  4  shows  the  arrangement  used  when  shallow 
bowl  fixtures  are  employed,  it  being  necessary  here  to  install  the  lamps 
and  reflectors  in  a  horizontalj)osition.  The  small  lamp  which  lights  the 


154  HANDBOOK  OF  ELECTRICAL  METHODS 

bowl  is  suspended  at  the  center  of  the  equipment  and  usually  consumes 
about  10  per  cent,  of  the  total  wattage  of  the  fixture.  Note  that  in  all 
cases  the  equipment  is  suspended  from  the  edge  of  the  fixture. 

A  very  artistic  effect  can  be  secured  by  properly  choosing  the  patterns 
and  colors  employed,  the  color  of  the  bowl  being  determined  either  by 
that  of  the  glass  or  that  of  the  illuminating  bulb. 

Cleaning  is  accomplished  in  the  single-unit  fixture  by  releasing  the 
chain  at  one  of  the  suspension  points.  In  the  multi-unit  fixture  the  re- 
flectors are  readily  accessible  in  their  normal  positions  except  where  hori- 
zontal as  in  the  case  of  the  shallow-bowl  equipment,  where  they  may  be 
released  by  a  spring  catch  and  tilted  into  an  accessible  position.  These 
reflectors  have  a  fire-glazed  inner  surface  so  that  dust  may  easily  be  re- 
moved with  a  damp  cloth.  Should  it  be  necessary  to  clean  the  bowl, 
it  can  be  released  either  by  set-screws  or  the  entire  interior  equipment 
can  be  lifted  clear  of  the  bowl. 


VIII 

TRANSFORMERS,  OIL  SWITCHES  AND   CIRCUIT- 
BREAKERS 

Testing,  Operation  and  Arrangements  of  Transformers,  Protection  of 
Secondary  Networks,  Maintenance  of  Oil  Switches  and  Circuit-breakers 

Testing  Transformers  for  Insulation  (By  T.  W.  Poppe). — Central- 
station  managers  in  small  towns  are  often  worried  about  the  possible 
breakdown  of  the  insulation  of  transformers,  which  might  cause  fires  in 
buildings  by  coming  in  contact  through  the  house  wires,  with  gas  pipe  at 
the  outlet  of  the  chandelier  or  other  possible  grounds  or  shock  customers 
in  the  act  of  turning  on  the  circuit  at  a  brass  lamp  socket.  All  trans- 
formers should,  therefore,  be  tested  occasionally  to  make  sure  the  insula- 
tion is  perfect.  This  should  be  done  when  the  transformer  is  inspected 
to  see  if  the  proper  amount  of  oil  surrounds  the  windings.  It  is  then  a 
simple  and  easy  matter  and  should  not  be  neglected.  The  following  is  a 


Thuin 
Screv 


r~ 


•Boards 


Fuse  Wti 
FIGS.    1  AND  2. TESTING  TRANSFORMERS  FOR  INSULATION. 

description  of  how  transformers  can  be  tested  on  the  ordinary  2300-volt 
line,  disconnecting  the  consumer  from  service  only  a  few  minutes  if  the 
transformer  insulation  proves  to  be  sound.  It  it  proves  otherwise  it  is 
well  to  disconnect  the  transformer  from  service  for  such  time  as  is  required 
to  install  a  new  one.  Fig.  1  shows  a  handy  fuse  block  suitable  for  this 
purpose.  It  is  constructed  of  two  pieces  of  wood  1  in.  thick,  3  in.  wide 
and  12  in.  long.  The  two  pieces  of  wood  are  clamped  together,  as  shown, 
by  means  of  thumb-screws  and  bolts.  Between  these  blocks  and  fast- 
ened as  shown  in  Fig.  2  a  piece  of  1/4-amp.  or  1/8-amp.  fuse  wire  10  in. 
long  should  be  fastened.  Under  the  locknuts  and  washers  shown  in 
Fig.  2  a  piece  of  copper  wire  should  be  attached.  This  forms  a  cheap, 
ready-made  fuse  block  which  can  be  thrown  about  without  danger  of 
breakage.  The  lineman  can  readily  fasten  it  to  his  belt  by  means  of  the 
copper  wire  when  climbing  the  pole.  The  fuse  block  should  be  attached 

155 


156 


HANDBOOK  OF  ELECTRICAL  METHODS 


to  one  of  the  primary  wires  and  to  one  of  the  secondary  wires,  as  shown  in 
Fig.  3.  Should  the  secondary  be  connected  to  ground  the  ground  con- 
nection should  be  disconnected.  In  small  towns  the  secondary  is  rarely 
connected  to  ground.  Were  the  ground  connection  allowed  to  remain 
in  place  while  making  a  test  the  result  might  be  misleading  should  a 
ground  exist  on  the  opposite  primary  line.  After  connecting  the  fuse 
block  as  shown  the  fuse  plug  No.  1  protecting  the  transformer  should  be 
withdrawn  from  its  receptacle.  Should  the  insulation  of  the  transformer 


First 
Connections,. 


Fuse  Block 


Second  -  —  ». 

|  1 

i 

onnections 

v%" 

^  Plug  No.l 

Secondary 

gj        g    Primary 

•^    F      a 

FIG.    3. TESTING  TRANSFORMERS  FOR  INSULATION. 

be  defective  the  current  would  flow  through  the  defect  into  the  secondary 
coils  and  through  the  fuse  wire  into  the  other  primary  line.  This  would 
cause  the  fuse  to  blow,  showing  that  the  transformer  insulation  is  de- 
fective. No  fear  need  be  felt  about  throwing  a  short-circuit  on  the  line 
through  the  fuse  block,  as  the  load  1/8  amp.  or  1/4  amp.  would  do  no 
harm  should  the  insulation  allow  the  current  to  flow.  The  connection  to 
the  primary  line  should  now  be  transposed,  placing  it  upon  the  other  pri- 
mary line,  withdrawing  fuse  plug  No.  2  and  reinstating  fuse  plug  No.  1. 
This  is  done  because  it  is  possible  that  a  slight  defect  may  exist  in  a  part 


Plug 


Plug 


trneter 
"ransformer 


Voltmefce 


FIG.    4. TESTING  TRANSFORMERS  FOR  INSULATION. 

of  the  windings  which  might  have  sufficient  self-induction  to  choke  the 
circuit  when  connections  to  the  first  primary  line  are  made.  When  the 
transposition  is  made  it  lessens  the  self-induction  and  should  the  defect 
exist  the  fuse  will  blow.  Should  one  fear  using  the  fuse  block  the  same 
connections  can  be  made  by  using  the  fuse  block  in  series  with  a  volt- 
meter and  shunt  transformer  as  shown  in  Fig.  4.  This  would  be  abso- 
lutely safe,  but  a  low  reading  on  the  voltmeter  should  not  be  neglected, 
as  it  indicates  that  a  defect  exists  and  should  be  attended  to. 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS    157 

Current-ratio  and  Phase-angle  Test  of  Series  Transformers  (By 
H.  S.  Baker). — The  method  here  described  for  determining  the  current- 
ratio  and  phase  angle  of  series  transformers  consists  in  bucking  a  known 
multiple  of  the  primary  amperes  against  another  known  multiple  of  the 
secondary  amperes  and  reading  the  vector  difference  upon  a  wattmeter. 
The  only  apparatus  required  consists  of  a  wattmeter  of  the  moving-coil 
type,  an  ammeter,  a  laminated  iron  ring  upon  which  may  be  wound 


Watt  Meter 
Lamp  Bank 

FIG.    1. CURRENT-RATIO  AND  PHASE-ANGLE  TEST  OF  SERIES  TRANSFORMERS. 

various  numbers  of  turns  of  wire,  and  a  lamp  bank.  There  must  also  be 
available  a  source  of  polyphase  e.m.f.,  a  source  of  heavy  current  and 
switches,  as  shown  in  Fig.  1. 

The  procedure  of  test  is  as  follows:  The  apparatus  is  connected  as 
shown  in  Fig.  1.  The  test  ring  shown  has  one  primary  turn,  with 
secondary  turns,  shown  in  full  line  wound  approximately  uniformly 
around  the  ring.  The  tertiary  winding,  shown  in  dotted  line,  is  also 
wound  approximately  uniformly  around  ring.  This  tertiary  winding 
feeds  through  the  switch  B  directly  into  the  moving  coil  of  the  watt- 
meter. 


158 


HANDBOOK  OF  ELECTRICAL  METHODS 


Voltage  taps  are  taken  off  at  the  secondary  terminals  of  the  trans- 
former under  test  and  connected  through  the  switch  C  to  the  moving 
coil  of  the  wattmeter  through  the  regular  meter  resistance  shown. 
The  series  coil  of  the  wattmeter  is  supplied  with  5  amp.,  which  may 
be  taken  from  either  of  two  e.m.f.  phases  through  the  switch  A,  and 
may  be  reversed  at  will  by  means  of  the  switch  D. 

Current  is  supplied  through  the  heavy  current  circuits  as  shown. 
Care  should  be  taken  that  the  primary  and  secondary  amperes  are 
bucking  in  the  test  ring  and  not  adding.  The  switches  A  and  B  are 
closed  to  the  right  and  the  switch  D  closed  in  the  direction  giving  a  plus 
deflection  on  the  wattmeter.  If  D  is  to  the  right  the  reading  may  be 
designated  plus  and  if  to  the  left  minus.  The  switch  A  is  then  closed  to 
the  left  and  another  reading  taken. 

The  above  two  readings  represent  components  of  tertiary  amperes 
along  directions  of  the  two  e.m.f  s.  used.  The  series  secondary  terminal 
voltage  may  now  be  read  as  follows : 

Close  the  switches  A  and  C  to  the  right  and  the  switch  D  in  the 
direction  to  give  a  plus  deflection  of  the  wattmeter.  Read  the  watt- 
meter and  then  throw  switch  A  to  the  left  and  repeat  the  reading.  These 
two  readings  represent  components  of  secondary  terminal  volts  along  the 
same  two  directions. 

The  above  four  readings  were  as  follows  in  the  case  of  a  series  trans- 
former marked  400  to  5  amp.,  a  test  ring  with  two  primary  turns  being 
used: 


Ring 
secondary 
turns 

Secondary 
amperes 

Tertiary  current 

Secondary  volts 

R 

L 

R 

L 

161 
162 
163 

3.6 
3.6 
3.6 

-89 
-22 

+47 

-22 

+46 

+  118 

+4.0 
+4.4 
+4.9 

+  1.3 
+  1.6 
+2.0 

Fig.  2  is  a  diagram  in  which  the  above  readings  are  plotted  for  161, 
162  and  163  turns.  The  lines  OR  and  OL  are  60  deg.  apart,  representing 
two  sides  of  the  three-phase  e.m.f.  supply  shown  in  Fig.  1.  OL  was 
assigned  the  e.m.f.  phase  which  leads  OR  in  order  to  give  the  diagram 
correct  rotation.  The  point  161  was  determined  by  measuring  along 
OR  a  distance  (see  table)  of  minus  89  and  erecting  a  perpendicular  to 
OR,  then  measuring  along  OL  a  distance  of  minus  22  and  erecting  a 
perpendicular  to  OL. 

The  intersection  of  these  perpendiculars  gives  the  point  161,  and 
the  vector  0 — 161  is  the  only  line  having  projections  along  OR  and  OL 
of  the  values  of  minus  89  and  minus  22.  This  vector  thus  represents  the 
current  flowing  in  the  tertiary  winding  when  3.6  amp.  are  in  the  secondary 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS     159 


of  the  transformer  under  test,  and  when  161  to  2  is  the  ratio  of  the  turns 
on  the  test  ring.  Similarly,  the  points  162  and  163  are  plotted  from  the 
corresponding  readings. 

It  will  be  seen  that  adding  one  turn  to  the  secondary  of  the  test  ring 
changes  its  secondary  amp. -turns  in  magnitude  but  not  in  phase,  and  in 
going  from  161  to  162  the  point  has  passed  0.  At  the  interpolated  point 
161.81  the  vector  0  —  161.81  is  at  right  angles  to  the  secondary  amp.- 
turns  of  the  test  ring.  This  is  the  vector  difference  between  the  primary 
and  secondary  amp. -turns  of  the  test  ring.  At  this  point  the  test  ring 


FIG.    2. CURRENT-RATIO  AND  PHASE-ANGLE  TEST  OF  SERIES  TRANSFORMERS. 

secondary  and  primary  amp. -turns  are  of  closely  equal  magnitude  because 
their  vector  difference  is  approximately  perpendicular  to  both.  We 
know  then  that  the  vector  ratio  of  currents  is  2  to  161.81,  or  the  current 
ratio  is  in  error  by  1.81  -f- 160,  or  1.13  per  cent. 

The  phase  difference  between  the  primary  and  secondary  amperes 
is  determined  by  measuring  the  distance  0  —  161.81  and  dividing  it  by 
161.81  times  the  distance  161  —  162,  which  operation  gives  the  tangent 
of  the  angle  of  secondary  current  lead. 

The  voltage  delivered  by  the  transformer  under  test  is  determined 
by  plotting  the  voltage  points  x,  y  and  z  from  the  above  voltage  readings 
and  interpolating  between  x  and  y  in  the  same  ratio  as  the  point  161.81 
is  between  the  points  161  and  162.  The  voltage  at  this  interpolated 
point  will  be  found  to  be  4.4  volts.  The  secondary  amperes  were  taken 
as  3.6.  The  following  data  are  then  obtained  for  this  point: 


Secondary 
amperes 

3.60 


Secondary 
volts 

4.4 


Ratio 
161.81 


Phase 
lead 
0.89 

161.81 


160  HANDBOOK  OF  ELECTRICAL  METHODS 

Other  points  taken  on  this  same  test  were  as  follows : 


1.64 


1.45 


162.22 


162.53 


1.33 


162.22 


1.57 


162.53 


The  above  test  of  three  points  on  the  ratio  curve  was  carried  out  and 
plotted  by  convenient  means  in  forty  minutes  and  forms  a  method  at 
once  available  and  effective. 

Bridged  Spark-gaps  Protect  Transformer  Coils  (By  L.  N.  Parshall). 
—Much  trouble  was  formerly  experienced  on  the  transmission  line  which 
connects  St.  Paul,  Minn.,  with  the  Somerset  (Wis.)  water-power  plant 
of  the  St.  Croix  Power  Company,  due  to  transformer  coils  puncturing 
and  burning  out.  With  the  occurrence  of  lightning  discharges  the  end 
turns  of  the  coils  would  break  down,  although  the  damage  was  usually 


Transformers  Coils 


-14,500  V.— 


FIG.    1. — BRIDGED  SPARK-GAPS  TO  PROTECT  TRANSFORMER  COILS. 

localized  there.  Attempts  to  provide  increased  insulation  at  these 
points  availed  nothing.  It  was  noticed  that  either  the  coils  nearest  the 
line  side  or  those  nearest  the  neutral  tie  were  most  affected,  the  middle 
sections  rarely  suffering.  Further  observation  showed,  too,  that  the 
line-side  coils  usually  stood  the  brunt  of  the  damage.  The  transformers 
were  500-kw.,  six-coil  units,  star-connected,  as  shown  in  Fig.  1,  with 
8000-volt  primaries  and  14,500-volt  secondaries  arranged  to  give  a  delta 
pressure  of  25,000  volts.  At  the  suggestion  of  F.  R.  Cutcheon,  electrical 
superintendent  of  the  St.  Paul  Gas  Light  Company,  and  John  Pearson, 
superintendent  of  the  St.  Croix  plant,  the  experiment  was  finally  tried 
of  connecting  lightning-arrester  spark-gaps  across  the  coils  as  shown, 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS     161 

using  five-gap  arresters  to  bridge  each  2400-volt  interval.  These  gaps 
are  set  to  discharge  just  above  the  normal  working  pressure  on  the  coil. 
Use  of  the  arresters  after  several  years'  experience  has  proved  the  prac- 
tical solution  of  the  former  trouble  from  puncturing.  Any  potential 
that  accumulates  across  the  initial  coils  is  discharged  by  the  gaps  before 
its  pressure  can  rise  to  a  point  to  rupture  the  insulation.  Proof  of  this 
protective  action  is  given  by  the  sparks  which  from  time  to  time  are  seen 
to  pass  across  the  outside  gaps,  while  the  remainder  of  the  group  is  silent. 

Protecting  Secondary  Networks  against  Defective  Transformers  (By 
S.  D.  Sprong). — In  approaching  the  problem  of  eliminating  a  defective 
distributing  transformer  on  primary  circuits  without  allowing  it  to  re- 
main as  a  short-circuit  on  the  secondary  network,  the  author  dismissed 
from  consideration  differential  relays  with  contacts  and  all  other  devices 
suitable  for  interior  work.  This  process  of  elimination  left  but  one 
protective  device  that  might  be  employed,  namely,  the  fuse;  but  un- 
fortunately the  fuse  has  no  sense  of  discrimination  in  the  direction  of 
the  flow  of  current.  Therefore  it  remained  to  utilize  the  fuse  in  such  a 
way  as  to  make  it  respond  to  reverse  power,  regardless  of  direction. 
Apparently  the  only  means  of  doing  this  was  to  superpose  on  it  a  current 
resulting  only  from  the  reversal  of  load.  It  then  remained  so  to"  connect 
this  fuse  that  when  ruptured  by  reverse  power  it  would  disconnect  the 
transformer  secondary  from  the  network.  This  was  accomplished  by 
connecting  the  transformer  to  the  center  of  the  fuse  and  one  of  its  ter- 
minals respectively. 

The  connections  of  the  device  for  a  three-wire  network  are  shown 
in  Fig.  1.  The  commercial  transformer  is  shown  at  A,  one  terminal 
of  the  primary  being  connected  in  series  with  a  coil  B  of  the  series  in- 
strument transformer.  The  terminals  of  the  secondary  of  the  commer- 
cial transformer  are  connected  through  coils  C  and  C\  on  the  series  trans- 
former. These  latter  coils  are  connected  to  the  middle  point  of  the 
looped  fuses  D  and  DI,  one  side  of  which  is  connected  from  E  and  E\ 
to  the  outer  conductors  of  the  three-wire  network.  The  fuses  D  and  DI 
act  as  a  short-circuit  connection  on  the  coils  E  and  E\.  Under  normal 
conditions  the  primary  B  and  secondary  coils  C  and  Ci,  having  the 
same  ampere  turns  and  being  connected  in  opposition,  will  neutralize 
each  other  so  that  there  will  be  no  m.m.f.  circulating  in  the  core  of  the 
series  transformers  to  energize  the  coils  E  and  E\.  This  balance  of 
conditions  is  maintained  at  all  loads  and  is  upset  only  by  a  reverse 
current  flowing  from  the  secondary  network  into  the  transformer  such 
as  is  occasioned  by  a  short-circuit  in  the  latter.  Such  a  condition  re- 
verses the  relative  polarity  of  the  coils  C  and  Ci,  thus  energizing  the 
core  and  causing  a  heavy  short-circuit  current  to  flow  through  the  coils 
E  and  EI  by  way  of  the  short-circuiting  fuses  D  and  DI.  The  heavy 


162 


HANDBOOK  OF  ELECTRICAL  METHODS 


short-circuit  current  through  the  fuse  immediately  ruptures  them  and 
isolates  the  main  terminals  at  G  and  G\. 

This  device  has  been  built  and  tested  in  transformers  ranging  from 
5  kw.  to  50  kw.,  two-wire  and  three- wire.  It  operates  so  nearly  instan- 
taneously that  it  does  not  blow  the  primary  fuses  in  transformers  im- 
mediately adjacent.  The  fuses  D  and  DI  each  carry  the  secondary  cur- 
rent and  under  normal  working  conditions  are  so  proportioned  that 
they  will  not  blow  from  overload.  Their  current-carrying  capacity 
compared  with  the  full  load  of  the  transformer  is  not  less  than  five  to 
one.  In  other  words,  the  short-circuit  current  available  to  blow  this 
fuse  in  case  of  reversal  is  at  least  five  times  the  full-load  secondary 


FIG.    1. PROTECTING  SECONDARY  NETWORKS  AGAINST  DEFECTIVE  TRANSFORMERS. 

current  of  the  transformer.  Various  tests  have  been  made  in  the  degree 
of  short-circuit  in  the  commercial  transformer,  varying  from  a  direct 
short-circuit  across  its  primary  terminals  to  a  partial  short-circuit  on 
the  secondary  winding.  The  protecting  fuses  D  and  Z>i  blow  in  every 
case  and  almost  instantaneously  even  on  the  minor  short-circuits  in 
the  secondary  of  the  transformer.  The  device  operates  so  effectively 
that  on  a  few  tests  a  short-circuit  in  the  commercial  transformer  of 
such  proportions  as  not  to  blow  the  primary  fuse  did  blow  the  pro- 
tector fuse.  This,  however,  results  very  infrequently  and  was  due  to 
the  very  nice  balance  of  conditions  that  occurred  in  some  of  the  tests. 

Inserting  Spare  Transformer  in  Star-delta  Group. — A  fourth  spare 
unit  is  included  in  the  bank  of  transformers  which  furnish  energy  for 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS    163 


the  various  motors  about  the  new  9000-kw.  steam-turbine  plant  of  the 
Laclede  Gas  Company,  St.  Louis.  The  primary  windings  of  these  trans- 
formers are  connected  in  star  and  the  secondaries  in  delta.  Switching 
provision  has  been  made  by  William  Bradford,  electrical  engineer  for 
the  company,  so  that  the  spare  transformer  can  be  immediately  connected 
in  place  of  any  of  the  other  units  which  may  burn  out  or  break  down. 
The  scheme  used  is  illustrated  in  the  sketch,  Fig.  1.  For  the  star  con- 
nection three  single-pole,  double-throw  switches  are  required,  while 
for  the  delta  transfer  double-pole,  double-throw  switches  are  needed. 


v. 


Primary 
Star 


S.P.D.T. 
Switches 

Spare 
Transformer 


FIG.    1. INSEKTING  SPARE  TRANSFORMER  IN  STAR-DELTA  GROUP. 

The  corresponding  primary  and  secondary  switches  are  mounted  in 
line  on  the  board,  so  that  both  windings  of  the  spare  unit  will  be  auto- 
matically connected  to  the  proper  phase.  The  switch  panel  for  effecting 
this  transfer  is  mounted  directly  in  front  of  the  transformer  bank  in  the 
basement. 

Operation  of  Tub -transformer  Secondaries  in  Series. — At  one  of 
the  Omaha  company's  substations  it  happened  that  there  was  a  long 
and  heavily  loaded  6.6-amp.  inclosed-arc  circuit,  and  near  by  another 
similar  circuit  very  much  underloaded.  From  the  position  of  the  lines 
and  the  streets  they  served,  it  would  have  been  inexpedient  to  transfer 
lamps  from  the  heavily  loaded  circuit  onto  the  shorter  one.  The  sim- 
plest connection,  therefore,  seemed  that  of  plugging  the  two  circuits  in 
series  at  the  board  and  feeding  the  pair  from  their  30-kw.  constant- 


164 


HANDBOOK  OF  ELECTRICAL  METHODS 


current  transformers  similarly  connected  in  series.  After  some  mis- 
givings, this  was  successfully  accomplished,  and  the  two  tub  trans- 
formers now  pull  along  together  without  any  signs  of  trouble.  In  con- 
necting up  these  transformers  with  their  primaries  in  parallel  and  their 
secondaries  in  series  it  was  quickly  found  that  identical  polarity  arrange- 
ments must  be  preserved  throughout.  With  the  two  tubs  free  to  regulate 
separately,  objectionable  hunting  occurred.  A  slight  change  in  the  ex- 
ternal circuit  would  cause  unequal  compensation  in  the  two  units,  and 
then  both  would  oscillate  in  supplemental  fashion,  giving  poor  regula- 
tion. This  " hunting"  was  finally  avoided  by  tying  the  floating-coil 


FIG.    1. OPERATION  OF  TUB-TRANSFORMER  SECONDARIES  IN  SERIES. 

system  of  one  firmly  in  full-load  position,  depending  on  the  regulation 
of  the  other  to  control  the  circuit.  A  similar  scheme  has  since  been 
applied  to  the  test  transformers  in  the  company's  lamp-test  department, 
when  heavy  series  loads  are  to  be  carried.  A  wiring  diagram  of  this 
scheme  appears  in  the  upper  Fig.  1. 

Paralleling  Transformer  Banks  on  Star-delta  Systems  (By  R.  E. 
Cunningham). — An  interesting  condition  arises  when  it  is  necessary  to 


oih V 

UUL8Jl£fl£MQj 


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fiftnn 

[*  —  — 


Test  Transformer 
and  Voltmeter 


V.M. 
FIG.    1. PARALLELING  TRANSFORMER  BANKS  ON  STAR-DELTA  SYSTEMS. 

connect  in  parallel  two  transformer  banks  operating  on  a  star-delta  sys- 
tem. Assume  a  case  where  there  is  a  star-connected  transmission  system 
and  it  is  required  to  install  a  bank  of  three  transformers  to  feed  into  a 
delta  distributing  system.  Fig.  1  shows  the  various  connections  which 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS     165 

may  be  made,  while  Fig.  2  shows  diagrammatic  ally  the  two  different 
phase  relations  produced  by  these  connections. 

It  will  be  noted  from  Fig.  2  that  the  two  different  deltas  produced 
will  not  parallel,  regardless  of  what  combination  of  leads  is  made.  These 
two  deltas  are  produced  by  either  a  " right-hand"  or  a  " left-hand" 
connection  of  the  primary  coils,  or  by  the  two  possible  connections  of  the 
secondaries. 

Where  the  transformer  banks  to  be  paralleled  are  of  the  same  type, 
and  it  is  possible  to  trace  out  the  connections  of  both  the  primaries  and 
the  secondaries  and  make  exactly  duplicate  arrangement  of  connections, 
there  will  be  no  danger  from  throwing  the  two  banks  together  without 


b  a       ac 


a'       a' 


FIG.    2. PARALLELING  TRANSFORMER  BANKS  ON  STAR-DELTA  SYSTEMS. 


making  preliminary  tests.  But  if  it  is  impossible  to  trace  out  the  con- 
nections, on  account  of  the  leads  being  brought  out  underground,  or  if  it 
is  required  to  connect  in  parallel  with  transformers  in  a  distant  sub- 
station, a  "  phasing-out "  test  must  be  made.  For  this  test  two  shunt 
instrument  transformers,  of  the  same  voltage  as  the  secondaries  of  the 
main  transformers,  and  two  voltmeters  should  be  used.  For  convenience 
in  making  this  test  the  three  leads  of  the  two  lines  to  be  paralleled  should 
be  tagged  a,  b,  c  and  1,  2,  3  respectively.  By  testing  out  the  various 
combinations  of  leads  as  shown  in  the  accompanying  table,  it  can  be 
quickly  determined  whether  proper  connections  have  been  made  for 
paralleling. 


1     2     3 

a     b     c 

1     2     3 

b     c     a 

1     2     3 
cab 

123 

c     b     a 

123 

a     c     b 

I     2     3 

b     a     c 

This  table  shows  the  six  possible  combinations,  the  tests  being  made 
by  connecting  one  testing  transformer  from  1  to  a,  the  other  from  2  to  b, 
or  3  to  c,  etc. 


166 


HANDBOOK  OF  ELECTRICAL  METHODS 


If  all  of  the  above  combinations  are  tested  out  without  finding  one 
which  gives  "no  voltage"  between  the  respective  leads,  it  is  obvious  that 
the  two  transformer  banks  will  not  parallel,  and  the  connection  on  one 
of  the  banks  will  have  to  be  reversed  according  to  Fig.  1. 

The  new  connections  having  been  made  the  series  of  tests,  as  shown 
in  the  table,  should  again  be  made  and  one  of  the  combinations  will  be 
found  which  will  give  "no  voltage"  across  the  three  respective  leads. 

Two  testing  transformers  are  necessary,  as  there  are  certain  of  the 
combinations  of  leads  which  will  give  double-line  voltage,  which  will 
cause  both  voltmeters  to  show  full  voltage. 

The  Three -transformer  Method  of  Changing  from  Two  to  Three 
Phases  (By  F.  T.  Wyman). — The  method  in  common  use  for  changing 
from  two  phases  to  three  phases,  or  the  reverse,  is  one  involving  the  use 
of  two  transformers  with  either  the  secondaries  or  primaries  T-connected. 
In  this  method,  which  is  illustrated  in  Fig.  1,  the  voltages  are  subject 


-3  Phase 


D' 

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3       C 
3      C 

Phase 
A 

E 

0 

1   1 

1  € 

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Phase  B 


FIG.    1. TRANSFORMATION  WITH  TWO  TRANSFORMERS. 

to  distortion  not  only  when  secondary  loads  are  unbalanced,  but  also 
under  balanced  non-inductive  loads.  If  one  of  the  transformers  becomes 
inoperative,  then  only  one  phase  remains  active  on  either  the  three-phase 
or  the  two-phase  side,  so  that  the  whole  system  is  out  of  commission  until 
a  new  transformer  can  be  installed.  Consequently,  in  order  to  insure 
continuity  of  service  a  spare  transformer  must  be  continually  carried  in 
stock. 

A  three-transformer  method  of  obtaining  the  same  results,  which 
seems  to  possess  some  merits,  although  it  has  not  been  applied  practically 
to  any  great  extent,  is  shown  in  Fig.  2.  The  transformers  are  shown  A- 
connected  on  both  the  primary  and  secondary  sides,  although  the  trans- 
mission-line side  can  be  either  A-connected  or  Y-connected  as  the  require- 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS     167 

ments  of  transmission  demand,  and  the  neutral  of  the  Y-connected 
system  may  be  grounded  if  desired. 

In  comparison  with  the  two-transformer  method,  the  three-trans- 
former method  possesses  the  advantage  of  allowing  the  two-phase  volt- 
ages to  be  obtained  from  the  same  transformer  coils  connected  for  and 
delivering  three-phase  voltages;  however,  the  two-phase  voltages  are 
not  equal  in  value  to  the  three-phase  voltages  and  the  ratio  is  not  a 
convenient  one,  being  1.00  to  0.866  =  1.155  to  1.00. 

If  one  of  the  transformers  in  the  three-transformer  system  should 
become  inoperative,  then  the  two  remaining  ones  can  immediately  be 
temporarily  V-connected  and  carry  the  load  until  the  other  is  repaired, 


Transmissi 


FIG.    2. TRANSFORMATION  WITH  THREE  TRANSFORMERS. 

thus  avoiding  the  necessity  of  carrying  a  spare  transformer  in  stock. 
When  a  spare  transformer  is  kept  in  stock  its  rating  is  only  two-thirds 
as  great  as  a  spare  transformer  for  a  two-transformer  scheme. 

The  three-transformer  scheme  possesses  a  disadvantage  as  compared 
with  the  two-transformer  scheme  in  that  " inter-connected"  two-phase 
generators  or  motors  cannot  be  used,  as  destructive  local  currents  would 
be  produced  in  the  windings.  It  is  superior  to  the  two-transformer 
scheme  in  its  greater  freedom  from  unbalancing  of  voltage  and  larger 
factor  of  safety  for  continuity  of  service. 

Low-freezing  Mixtures  for  Oil  Switches  (By  F.  W.  HARRIS). — It  is 
common  for  oil  switches  to  be  so  located  that  they  are  exposed  to  extreme 
cold.  The  effect  on  the  ordinary  transformer  or  switch  oil  is  first  to 
render  it  very  thick  and  at  very  low  temperatures  actually  to  solidify  it. 
Even  if  it  is  reduced  to  the  consistency  of  a  thick  jelly  it  is  likely  to  inter- 
fere seriously  with  switch  operation,  and  it  is  desirable  in  switches  so 
exposed  to  provide  a  liquid  that  is  not  open  to  this  objection.  There 
are  now  on  the  market  several  oils  that  have  very  low  freezing  points.  In 
this  connection  it  is  desirable  to  point  out  that  were  it  not  for  two  fea- 
tures tetrachloride  of  carbon  would  be  far  superior  to  any  oil  for  use  in 
12 


168 


HANDBOOK  OF  ELECTRICAL  METHODS 


such  switches.  It  is  not  inflammable  and  does  not  produce  inflammable 
vapors  and  it  has  a  very  low  freezing  point.  It  is,  however,  rather  ex- 
pensive, about  seven  times  as  expensive  as  a  good  oil,  and  it  is  volatile, 
producing  disagreeable  vapors  at  a  relatively  low  temperature.  It  is 
probable  that  if  the  matter  of  price  could  be  corrected  it  would  come 
into  very  general  use  for  this  purpose,  special  switches  being  arranged 
for  it.  It  is  valuable  for  reducing  the  freezing  point  of  oil,  and  a  half- 
and-half  mixture  will  not  stiffen  up  appreciably  at  20  deg.  below  zero  C. 
It  must  however  be  watched  as  it  evaporates  and  its  use  is  not  to  be 
commended  at  this  time. 

Turpentine,  however,  may  be  used  with  good  effect.  A  half-and-half 
mixture  of  good  turpentine  and  ordinary  transformer  oil  will  freeze  at 
about  —30  deg.  C.  It  does  not  materially  lower  the  breakdown  voltage 
and  is  not  harmful  owing  to  carbonization  in  breaking  the  circuit.  It  is 
inflammable  and  evaporates,  but  the  standard  low-freezing  mixtures 
and  oils  also  do  that.  It  used  to  be  the  practice  to  use  on  the  outdoor 
switches  of  the  New  York,  New  Haven  &  Hartford  Railroad  a  low-freezing 
oil  in  the  winter  and  to  take  it  out  in  the  spring  and  use  standard  oil  in 
the  summer.  When  operators  have  trouble  with  switches  freezing  this 
turpentine  mixture  is  a  good  one  to  know  about,  and  if  a  little  care  is 
used  no  harmful  results  need  be  feared.  It  is  probably  too  volatile  for 
summer  use,  however,  and  should  be  removed  in  the  spring  before  the 
warm  days  come. 

Disconnect  Coupling  for  Oil-switch  Leads. — In  the  installation  of  oil 
switches,  lack  of  space  or  other  conditions  sometimes  make  it  impossible 
to  locate  disconnect  switches  between  the  oil  switch  and  bus,  where  the 


Set  Screw 
Wood. Plug 


Union  Butt 

Joint/ 


ard-rubber 
Tubing 

t  Screw 


^ To  Bus 

FIG.    1. DISCONNECT  COUPLING  FOR  OIL  SWITCH  LEADS. 

use  of  such  switches  would  be  advisable  to  render  the  oil  switch  "dead" 
for  adjustment  or  repairs.  This  condition  existed  in  the  2300-volt  sta- 
tion of  the  Anaconda  Mining  Company  at  Butte,  Mont.,  where  the  300- 
amp.  oil  switches  were  installed  with  terminals  connected  directly  through 
vertical  leads  to  the  buses.  To  take  the  place  of  disconnect  knife 
switches  and  make  possible  repairs  on  the  apparatus,  Mr.  W.  S.  Guthrie. 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS    169 


chief  electrician,  designed  the  insulated  joint  feature  Fig.  1,  page  168, 
the  special  fittings  being  made  on  order  by  the  manufacturer  of  the  solder- 
less  fittings  used.  In  place  of  the  usual  solid  hexagon  nut  employed  on 
ordinary  Dossert  couplings,  the  fitting  is  broken  into  two  parts  held  to- 
gether by  a  union  nut  coupling,  which  makes  a  firm  butt  contact  between 
the  1-in.  flat  bearing  surfaces.  This  nut  can  be  unscrewed  with  an  in- 
sulated-handle wrench,  opening  the  line  and  disconnecting  the  device. 
The  connector  parts  are  protected  against  short-circuit  or  accidental 
contact  by  the  hard-rubber  covering  shown.  After  investigating  the 
cost  of  special  hard-rubber  castings  for  the  purpose  and  finding  the  ex- 
pense of  these  such  as  to  make  them  out  of  the  question,  Mr.  Guthrie 
was  able  to  utilize  stock  rubber  tubing  1.75  in.  in  diameter,  cut  into  6- 
in.  lengths.  These  tube  sections  are  held  in  position  by  the  filled-wood 
cap  pieces,  which  are  in  turn  fixed  in  place  by  small  set-screws.  To  gain 
access  to  the  connector  it  is  necessary  merely  to  remove  the  upper  screw, 
allowing  the  tube  section  to  drop  down  out  of  the  way  so  that  the  hexagon 
nut  can  be  gripped  with  the  insulated  wrench. 


Handle 


Pivot 


Pivot 


Pivot 


p.pe 


Pivot 


Pivot 


Handle 


Pivot 


To  Switch 


1 

Buckled  Position 

l"Pipe 

—  —  -^^ 

^~ 

Pivot@-< 

Pivot 


FIGS.    1  AND  2. CORRECT  AND  INCORRECT  ARRANGEMENT_OF  SWITCH  PULL-RODS. 

Switch  Pull-rods  in  Tension,  Not  Compression.— The  oil  switches  in 
a  certain  substation  had  given  trouble  ever  since  the  time  of  their  erec- 
tion. They  were  operated  by  long  rod-and-lever  connections  as  shown 
in  Figs.  1  and  2,  and  the  switches  controlled  a  25,000-vol  three-phase 
line.  The  difficulty  seemed  to  be  that  the  operators  continually  broke 
down  the  castings  of  the  mechanism,  effecting  automatic  release  from 
the  handle.  Complaint  was  made,  too,  that  the  switches  were  hard  to 
open  and  close. 


170  HANDBOOK  OF  ELECTRICAL  METHODS 

After  investigation  it  was  found  that  the  levers  and  pull-rods  had  been 
wrongly  connected,  the  arrangement  being  such  as  shown  in  Fig.  2,  which 
placed  the  long  1-in.  pipe  in  compression  when  the  switches  were  being 
closed.  This  caused  that  part  to  sag,  jamming  and  blocking  the  mechan- 
ism. The  rods  were  then  overhauled  and  converted  to  the  arrangement 
shown  in  Fig.  1,  a  spring  being  added,  thus  putting  the  parts  intension 
during  operation.  Since  this  change  was  made  the  switches  have  worked 
easily  and  without  further  trouble. 

Troubles  Due  to  Non-use  of  Circuit -breakers  (By  F.  W.  Harris).— 
A  common  source  of  complaint  is  the  heating  of  the  contacts  of  carbon 
circuit-breakers  after  they  have  been  in  service  for  a  long  period.  These 
breakers  usually  have  a  laminated  brush  made  up  of  thin  leaves  of  copper, 
and  any  temperature  over  a  certain  very  well-defined  maximum  will 
result  in  the  brush  becoming  soft  and  losing  its  elasticity.  Therefore  the 
heating  becomes  very  much  worse,  rapidly  resulting  in  the  ruin  of  the 
brush  and  sometimes  a  shut-down  of  the  plant.  Troubles  of  this  kind 
are  commonly  attributed  to  the  design  of  the  circuit-breaker  itself,  but  a 
great  deal  is  due  to  conditions  against  which  no  modifications  of  the  design 
could  be  expected  to  guard. 

Heating  of  contacts  is  very  noticeable  in  steel  mills,  and  one  case  of 
long-continued  trouble  resulted  in  dismantling  the  circuit-breakers  on 
three  successive  July  Fourths,  this  being  the  most  convenient  day  to  the 
mill  superintendent.  The  instruments  were  rated  at  10,000  amp.  and 
ran  on  a  load  much  below  this.  After  they  were  put  in  first-class  condi- 
tion they  ran  quite  cool  for  some  months,  the  heating  gradually  increas- 
ing until  they  had  to  be  overhauled  again.  An  examination  showed 
that  the  troublesome  circuit-breakers  were  connected  on  a  circuit  that 
was  never  opened  except  upon  dead-short-circuit  conditions,  and  that 
these  conditions  did  not  obtain  more  than  once  or  twice  a  year. 

The  trouble  was  traced  to  a  gradual  oxidation  of  the  contacts  and 
to  the  fact  that  the  troublesome  circuit-breakers  were  never  opened  and 
closed  to  rub  off  the  oxide.  It  was  found  that  if  the  instruments  were 
opened  and  closed  a  few  times  on  Sunday  it  was  possible  to  keep  the  con- 
tacts bright.  The  other  circuit-breakers  in  the  plant  were  naturally  sat- 
isfactory, as  they  opened  many  times  a  day  and  that  kept  the  contacts 
clean. 

In  general,  where  open  air-type  switches  are  not  operated  frequently 
it  is  an  excellent  plan  to  clean  them  with  emery  cloth  at  least  once  a 
month,  and  where  the  contacts  are  not  easily  accessible,  as  in  this  case, 
they  should  be  opened  and  closed  vigorously  say  a  dozen  times  once  a 
week. 

Temporary  Repair  to  Oil  Switch. — The  accompanying  Fig.  1,  shows 
the  temporary  repair  made  on  a  circuit-breaker  operating  handle  which 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS     171 


had  broken  down  at  the  catch  notches  designed  to  hold  the  handle  in  the 
closed  position.  Side  blocks  were  accordingly  made  the  same  shape  as 
the  notch  parts,  using  flat  pieces  of  iron.  These  side  pieces  were  then 
fixed  in  place  by  the  cotter  pins  which  hold  the  tripping  roller  inside. 
The  job  cost  little  to  carry  out,  and  will  keep  the  oil  switch  in  operation 
until  a  new  casting  can  be  secured. 


Operating 
Handle 


Break  at  Notch 
Hole  for  Pin 


Iron  Side  Piece 


'Cotter  for 

Tripping 

Roller 


FIG.    1. TEMPORARY  REPAIR  TO  OIL  SWITCH. 

Alarm  Connection  for  Transformers. — In  the  upper  Fig.  1,  page 
172,  alarm  circuits  are  shown  for  detecting  abnormal  rise  in  temperature, 
failure  of  cooling-water  supply  or  lowering  of  oil  level,  in  cases  where 
station  transformers  are  installed  at  points  remote  from  frequent  in- 
spection by  the  switchboard  operator.  By  the  arrangement  illustrated 
the  operator  can  test  his  oil,  water  and  temperature  without  leaving  his 
position.  The  water  alarm  is  provided  by  a  compression  element  in- 
serted in  the  inlet  line  so  that  as  long  as  pressure  is  on  the  piping  the 
contact  is  open.  If  pressure  fails  for  any  reason,  the  circuit  is  completed, 
ringing  the  alarm  bell  and  lighting  an  indicator  lamp.  A  generally 
similar  oil-level  float  alarm  is  installed  at  the  top  of  the  transformer 
tank  to  give  warning  of  lowering  of  the  oil.  Here  also  is  placed  a  ther- 
mometer with  an  electrical  contact  inserted  at  the  point  of  maximum 
allowable  temperature  rise.  If  the  transformer  becomes  overheated  the 
thermometer  circuit  will  be  completed,  also  giving  an  alarm.  The 


172 


HANDBOOK  OF  ELECTRICAL  METHODS 


switchboard  circuits  may  be  arranged  to  give  visible  and  audible  warning 
automatically,  or  the  attendant  may  be  required  to  make  regular  inspec- 
tions and  tests. 


I    Oil  Float  Alarm 

rH 

fl 

Oil  JJlLevel 

P 
1  Thermometer 

«~1 

ing  Coils 

Is 

MC^i 

S| 

t    , 

LC 

,  L 

^J 

"75 

,                                                       o  a 

„—,      „ 

6 

r                                                    u*-1 

Jl                                       1  Og>Bell 

S 

n 

I 

7 

By-Pass 

1 

1  Discharge  Pip^ 

- 

t                                                                                      1 

Cooling  Water 

FIG.    1. ALARM  CONNECTION  FOR  TRANSFORMERS. 

Two-phase  to  Three-phase  Auto -transformers  (By  Roy  E.  Uptegraff). 
— Occasionally  it  is  desired  to  transform  from  two-phase  to  three-phase 
or  three-phase  to  two-phase,  as  the  case  may  be,  to  run  a  three-phase 
motor  or  other  apparatus  from  a  two-phase  line,  or  vice  versa.  This  may 
be  accomplished  by  placing  on  each  leg  of  a  three-phase  core  single  wind- 
ings as  shown  in  Fig.  1.  Each  leg  is  wound  with  sufficient  turns  for  115.2 


1.1521 


FIGS.    1  AND  2. TWO-PHASE  TO  THREE-PHASE  AUTO-TRANSFORMERS. 

per  cent,  of  the  line  voltage,  and  taps  are  brought  out  for  100  per  cent, 
and  50  per  cent,  of  the  line  voltage  as  shown. 

For  a  better  understanding  of  the  two-phase  and  three-phase  relation, 
reference  should  be  made  to  Fig.  2.  Lines  1  and  4  and  2  and  3  in  the 
figure  represent  vectorally  the  two  phases  of  the  two-phase  circuit  since 
they  are  equal  in  length  and  at  right  angles  to  each  other,  the  two-phase 
angle  being  90  deg.  Lines  1  and  2,  2  and  3  and  3  and  1  are  equal  and  are 


TRANSFORMERS,  OIL  SWITCHES  AND  CIRCUIT-BREAKERS     173 

at  the  angle  of  60  deg.  with  each  other,  this  being  the  three-phase  delta 
angle. 

If  the  current  in  the  two-phase  side  be  represented  by  7,  the  current 
in  the  three-phase  lines  will  be  1.152  7,  neglecting  the  magnetizing  and 
loss  currents.  The  currents  in  the  three  legs  of  the  delta  are  not  equal 
but  are  as  shown  in  Fig.  1. 

The  winding  in  legs  A  and  B  required  for  100  per  cent,  of  the  voltage 
need  be  large  enough  for  only  7.6  per  cent,  of  the  two-phase  current, 
while  the  extra  15.2  per  cent,  of  the  winding  must  be  designed  for  50  per 
cent,  of  the  two-phase  current.  The  current  in  leg  C  must  be  designed 
for  50  per  cent,  of  the  line  current. 

In  explanation  of  the  different  currents  in  the  windings  it  will  be 
noted  first  that  in  Fig.  1  the  apex  of  the  delta  is  connected  to  one  three- 
phase  line  and  one  two-phase  line.  Since  the  currents  in  the  three-phase 
lines  are  equal  to  1.152  7  and  the  two-phase  current  is  7,  then  the  current 
in  the  upper  parts  of  sides  A  and  B  of  the  delta  is  1.152  7  —  7  =  0.152  7, 
or  0.076  7  in  A  and  B  each  from  the  apex  to  the  tap.  The  rest  of  the 
sides  A  and  B  must  be  designed  for  the  same  current  as  in  side  C,  as 
these  are  connected  in  series. 

As  the  whole  two-phase  current  flows  into  the  middle  of  side  C  as 
shown,  it  can  be  easily  seen  that  50  per  cent,  of  this  current  will  flow  in 
each  half  and  the  lower  parts  of  sides  A  and  B. 

The  size  of  standard  three-phase  transformer  parts  required  for  a 
two-phase-three-phase  auto-transformer  of  this  type  is  found  as  follows: 

The  value  of  the  kilovolt-amperes  in  the  sides  A  and  B  is  2(0.076  7 
X^+0.5  7X0.152  E)  10~3  =  0.304  7  #X10~3. 

The  kv.-a.  in  side  C  = 

0.5  7X1.152  #X10~3  =  0.576  7 

The  total  kv.-a.  in  the  windings  = 

0.304  7  #X10~3+0.576  7  #X10~3  =  0.88  7 

As  this  amount  of  power  is  transmitted  through  only  one  winding 
on  each  leg,  while  an  ordinary  two-coil  transformer  would  have  two 
windings  on  each  leg,  for  this  amount  of  power,  in  terms  of  an  ordinary 
transformer, 

0  88  7  E~>(  10~3 
the  rating  would  be  equal  to  —  —  =  0.44  7  #  X    10~3  in  kv.-a. 

z 

The  power  in  the  line  is  2  7  E  X   10~3.     Therefore,   the  rating  of  the 
auto-transformer  in  terms  of  a  standard  transformer  as  a  percentage 

of  the  line  kv.-a.  may  be  expressed  as  o~7~Fyri in- 3 =  ^2  per  cent. 

The  most  desirable  feature  of  the  above  auto-transformer  over  that 
of  other  methods  for  two-phase  to  three-phase  transformation,  according 
to  the  author's  point  of  view,  is  its  balanced  operating  condition.  This 
method  of  transformation  was  devised  by  William  T.  Taylor. 


IX 
INTERIOR  WIRING 

Methods  of  Wiring  Buildings  of  Different  Construction  and  Under 

Various  Atmospheric  Conditions,  Descriptions  of  Special 

Devices  and  Equipments 

Removing  Nails  from  Trim  in  Old -house  Wiring  (By  George  M. 
Talbot). — Before  replacing  finished  trim  that  has  been  removed  to  per- 
mit the  running  of  wires  the  nails  in  the  trim  should  be  cut  off  flush 
with  the  back  of  the  trim  with  a  pair  of  pliers  or  a  cold  chisel  (Fig.  1), 
or  should  be  broken  off  with  a  hammer.  If  an  attempt  is  made  to  drive 
them  out,  they  will  almost  invariably  chip  out  slivers  of  the  trim,  as 


FIGS.    1    AND    2. REMOVING  NAILS  FROM  TRIM  IN    OLD-HOUSE  WIRING. 

indicated  in  Fig.  2.     New  finishing  nails  of  small  diameter  should  be 
used  for  refastening  the  trim. 

Examining  Partition  Interiors  (By  Wm.  Sprunt). — A  pocket  flash- 
lamp  and  a  little  mirror  are  the  only  apparatus  required  to  inspect  the 


FIG.    1. EXAMINING  PARTITION  INTERIORS. 


interior  of  a  wall  or  partition  which  wrould  ordinarily  be  inaccessible. 
For  fishing  wires,  retrieving  cable  and  inspecting  finished  work,  this 
use  of  the  lamp  and  mirror  provides  a  labor-saving  "kink."  The 
mirror  has  only  to  be  introduced  in  the  outlet  hole  in  the  wall,  the 

174 


INTERIOR  WIRING 


175 


fiashlamp  and  eye  being  held  behind  it,  Fig  1,  page  174.  The  mirror 
reflects  the  light  of  the  lamp  onto  the  place  to  be  illuminated,  at  the  same 
time  reflecting  the  image  back  to  the  eye  near  the  lamp.  The  usefulness 
of  this  little  device  is  as  great  as  its  simplicity. 

Grounding  of  Bathroom  Fixtures,  Etc. — All  fixtures  installed  over  or 
near  damp  grounds,  earth  floors,  metal  steps,  radiators,  bathtubs,  wash- 
basins, etc.,  are  now  required  by  the  Omaha  city  electrical  inspection 
department  to  be  securely  grounded.  City  Electrician  Michaelsen  also 
recommends  generally  that  porcelain  receptacles  be  used  in  these  places 


FIG.    I. GROUNDING  OF  BATHROOM  FIXTURES. 

unless  such  sockets  detract  seriously  from  the  appearance  of  the  installa- 
tion, in  which  case  the  porcelain  proviso  is  waived.  As  a  protection 
against  any  part  of  bathroom  fixtures  becoming  charged  this  grounding 
ordinance  is  now  being  rigidly  enforced  in  Omaha  wherever  fixtures, 
sockets,  etc.,  are  near  enough  to  be  reached  or  touched  while  making 
contact  with  grounded  conductors.  (See  Fig.  1.) 

Support  of  Cables  for  Interior  Work. — It  frequently  happens  that 
cables  have  to  be  supported  beneath  ceilings  having  arched  construc- 
tion, and  supports  at  the  drop  beams  are  too  far  apart  to  keep  the  cable 
from  sagging  considerably.  A  simple  device  is  used  by  the  Freeman- 
Sweet  Company,  Chicago,  to  avoid  this  difficulty.  As  shown  in  the  ac- 
companying view,  Fig.  1),  the  cable  is  supported  at  the  drop  beams  in  the 
ordinary  manner.  Between  the  drop  beams  and  beneath  the  crest  of 
the  arch  a  cable  clamp  is  secured  to  the  cable  and  also  to  a  toggle-bolt 
which  may  be  shoved  through  a  small  hole  in  the  arch  above.  The 
toggle-bolt  is  of  the  collapsible  type,  and  all  that  is  necessary  to  install 


176 


HANDBOOK  OF  ELECTRICAL  METHODS 


it  is  to  drill  a  hole  just  large  enough  to  allow  the  head  of  the  toggle  to  slip 
through,  the  bolt  being  moved  around  until  the  toggle  opens.  This 
method  has  been  found  satisfactory  both  as  to  ease  of  installation  and 
as  to  the  result  obtained. 

/Flooring 


Cable 


ble  Clamp 


FIG.    1. SUPPORT  OF  CABLES  FOR  INTERIOR  WORK. 

Explosion-proof  Connector  Plug. — In  garages  and  other  places  con- 
taining explosive  gases  a  great  deal  of  risk  accompanies  attempts  to 
use  ordinary  insertion  plugs  for  making  temporary  connections.  A 


FIG.    1. — EXPLOSION-PROOF  CONNECTOR  PLUG. 

German  concern  which  owns  a  number  of  garages  has  made  experiments 
to  obtain  a  reliable  explosion-proof  plug.  The  one  shown  in  Fig.  1  was 
designed  by  one  of  its  engineers  and  has  been  submitted  to  exhaustive 
tests  at  the  Royal  Testing  Laboratories  at  Gross-Lichterfelde,  Germany, 
and  is  said  to  have  proved  very  satisfactory.  It  will  be  seen  that  in  making 
the  contact  the  pins  are  inserted  into  shells  of  insulating  material  sur- 


INTERIOR  WIRING 


177 


rounding  the  metal  part  of  the  receiver.  These  shells  fit  snugly  about 
the  contact  pins  so  that  when  the  connection  takes  place  the  surround- 
ing air  is  excluded.  As  a  further  precaution  there  is  an  outer  shell  around 
the  contact  pins  which  fits  into  an  outer  shell  of  the  receiver.  This 
excludes  the  air  even  before  the  pins  reach  the  inner  shells. 

The  Right  Way  to  Place  Protecting  Tubes  (By  G.  Converse).— A 
tube  for  protecting  a  wire  where  it  crosses  another  wire  should  always 
be  so  placed  that  the  tube  will  not  force  the  unprotected  wire  against 
the  surface  supporting  the  conductors.  The  tube  should  always  be  on 
the  inner  wire.  If  placed  on  the  outer  wire  the  tube  may  force  the  un- 
protected wire  against  the  surface  as  shown  in  Fig.  2.  Oftentimes 


•nr 


Inner  Wire" 

Bottom  View 


Outer  Wire 
Bottom  View 

FIGS.    1   AND  2. CORRECT  AND  INCORRECT  METHODS  OF  PLACING  TUBE. 


porcelain  tubes  are  used  on  wires  crossing  each  other  in  boiler-rooms  or 
locations  having  steam  pipes.  It  is  readily  seen  that  if  the  porcelain  tube 
is  placed  on  the  lower  instead  of  on  the  upper  wire  it  would  force  the 
upper  wire  against  the  hot  pipe,  with  the  result  that  the  insulation  would 
be  quickly  destroyed  and  a  ground  or  short-circuit  ensue. 

Right  and  Wrong  Methods  of  Connecting  Plug  Cut-outs  (By  H.  M. 
Sanders). — In  connecting  Edison  plug  cut-outs  they  should  always  be  so 
arranged  that  the  screw  shells,  which  extend  beyond  the  porcelain,  will 
not  be  alive  normally.  The  upper  Figs.  1  and  2  on  page  178  show  the 
right  and  wrong  methods  respectively.  If  connected  incorrectly,  there 
is  constant  danger  of  short-circuit  or  shock  when  men  are  working  about 
the  cut-outs  with  bare  wire  ends  or  tools.  Some  types  of  plug  cut-outs 
are  so  constructed  that  the  porcelain  is  higher  than  the  screw  shell,  which 
is  thereby  protected.  Such  cut-outs  would  be  properly  connected  as 
shown  in  either  I  or  II,  and  they  should  be  selected  where  possible. 

A  Method  of  Carrying  Wires  Around  Bridges  in  Old  Houses  (By  J.  G. 
Johns). — In  wiring  old  buildings  one  of  the  most  troublesome  tasks  is  to 
run  vertical  conductors  within  a  partition  space  between  studs  where 
the  normal  course  of  the  conductors  is  blocked  by  a  bridge.  If  the  space 


178 


HANDBOOK  OF  ELECTRICAL  METHODS 


between  studs  is  adjacent  to  a  doorway,  the  conductors  can  be  carried 
around  the  bridge  by  removing  the  jamb.  If  a  doorway  is  not  adjacent 
and  the  bridge  cannot  be  bored  through  from  above  with  a  long  boring 
tool,  because  of  obstructions,  it  is  necessary  to  cut  into  the  surface  of  the 
wall. 


Load 


^Edison  Plug  Cut-Out 

Correct  Method 


.Switch 


Load 


^-Edison  Plug  Cut-Out 

Incorrect  Method 


FIGS.    1  AND  2. RIGHT  AND  WRONG  METHODS  OF  CONNECTING  PLUG  CUT-OUTS. 


n 


n 


I     L -  Studs >i — 1 


—  \  —  1 

1 

—  

Knife  Slits 

~t- 

1 

through 

1 

Paper 

r\ 

1 

\ 

i  •> 

1- 

._^ 

^^ 

1 
1 
1 

1 

1 
H— 



/Bridge 


- 

,st 

ud 

S 

•'•: 
'•.' 

:  •' 

1 

™-; 

55 

/   , 

4 

mm, 

J 

\^s 

) 

_;' 

FIGS.   1  AND  2. METHOD  OF  CARRYING  WIRES  AROUND  BRIDGES  IN  OLD  HOUSES. 

With  certain  kinds  of  wall  paper  the  method  that  is  here  described 
can  be  used  with  practically  no  visible  damage.  If  moisture  will  dis- 
figure the  wall  paper,  however,  the  method  cannot  be  used.  Cartridge 
papers  are,  as  a  rule,  not  affected  by  a  little  water.  In  order  to  ascertain 


INTERIOR  WIRING 


179 


the  effect  of  water  on  the  paper  in  question,  it  will  be  necessary  to  experi- 
ment with  a  small  area  in  an  inconspicuous  corner  if  a  sample  of  the  paper 
cannot  be  had. 

If  the  paper  stands  the  test,  two  slits  should  be  cut  through  it  at 
right  angles  to  each  other,  see  lower  Fig.  1,  page  178,  at  a  point  just 
opposite  the  bridge  that  is  in  the  way.  The  bridge  can  be  located  by 
dropping  a  "  mouse  "  on  it  from  the  outlet  hole  cut  through  the  partition 
at  a  point  above  it.  A  sharp  knife  is  necessary  in  cutting  the  slits. 

The  paper  should  then  be  soaked  slightly  around  the  slits  with  a  wet 
sponge  or  cloth.  When  the  water  has  been  absorbed  by  the  paper  and 
the  paste  that  held  it  to  the  wall  has  softened,  peel  back  the  four  triangular 
sections  of  paper.  When  the  paper  is  completely  "  peeled"  it  .will  appear 
as  shown  in  Fig.  2.  Through  the  bared  plaster  cut  holes  into  the  parti- 
tion above  and  below  the  bridge,  and  remove  enough  plaster  from  in 
front  of  tfie  bridge  to  leave  a  cavity  that  will  accommodate  the  loom- 
covered  conductors.  The  conductors  may  then  be  run  in  as  suggested 
in  the  longitudinal  section  in  Fig.  2.  The  holes  left  in  the  wall  surface 
should  be  filled  with  plaster  of  paris  and  the  paper  carefully  replaced 
with  the  aid  of  a  flour  paste.  If  the  job  is  neatly  done  it  will  be  difficult 
to  find  where  the  paper  was  cut.  In  peeling  the  paper  from  the  wall  a 
wide-bladed  putty  knife  will  be  found  a  very  convenient  tool. 


Switch 


T 


-  + 


FIG.    1. 


Permanent 
Ground''' 

FIG.    2. 


Permanent  ""V, 

Ground  f 
FIG.    3. 

FIGS.    1,   2  AND  3. THE  USE  OF  SINGLE-POLE  SWITCHES. 

The  Use  of  Single-pole  Switches  (By  H.  G.  Clark) .—Single-pole 
switches  are  permitted  by  the  Underwriters  on  circuits  carrying  loads 
not  exceeding  660  watts  at  pressures  not  exceeding  250  volts.  This 


180  HANDBOOK  OF  ELECTRICAL  METHODS 

give.s  a  maximum  permissible  current  of  3  amp.  at  220  volts  or  6  amp. 
at  110  volts.  With  these  loads,  single-pole  switches  will  give  good  ser- 
vice in  residences  where  the  circuits  are  not  apt  to  be  disturbed,  but  in 
industrial  plants,  single-pole  switches  may  not  protect  from  trouble, 
and  it  is  good  practice  to  use  double-pole  switches  in  installations  where 
reliability  in  service  is  important.  Single-pole  switches  may  not  protect 
from  trouble  because  they  open  but  one  side  of  the  circuit.  In  Fig.  1, 
page  179,  if  one  side  of  a  two- wire  main  happens  to  be  grounded,  a  ground 
of  the  same  polarity  on  a  branch  circuit  controlled  by  the  single-pole 
switch  will  form  a  closed  circuit  around  the  switch.  If  the  grounds  are 
of  sufficiently  low  resistance,  enough  current  will  flow  to  light  the  lamps, 
even  with  the  switch  open.  If  the  resistance  of  the  grounds  is  high,  not 
enough  current  will  flow  to  light  the  lamps.  Furthermore,  with  condi- 
tions as  shown  in  Fig.  1,  if  a  wireman  accidentally  touches  a  wire  of  the 
positive  side  of  the  branch  circuit  to  any  grounded  object,  such  as  a  gas 
pipe,  a  short-circuit  will  result.  Single-pole  switches  in  two-wire  branches 
from  three-wire  mains  should  not  be  inserted  in  the  branch  wire  con- 
nected to  the  neutral  wire  of  a  three-wire  system  (Figs.  2  and  3).  The 
neutral  of  a  three-wire  system  is  usually  permanently  grounded  at  the 
central  station  as  well  as  elsewhere,  and  with  the  switches  in  a  neutral 
branch  wire  (Fig.  3),  trouble  is  more  apt  to  occur  than  when  the  switch 
is  in  the  other  branch  wire,  as  at  Fig.  2. 

One-piece  Versus  Two-piece  Push  Switches  (By  Eugene  E.  Smith). — 
In  electrical  installations  careful  study  should  be  made  of  all  points  in 
connection  with  the  materials  used  and  their  maintenance.  In  this 
connection  the  flush  push-switch  problem  is  often  overlooked,  and  the 
cheapest  article  is  often  selected,  with  bad  results.  The  field  of  push 
switches  is  wide,  and  prices  and  results  vary.  The  switches  are  divided 
into  two  general  groups,  the  one-piece  and  the  two-piece  switch;  by  this 
is  meant  one  in  which  the  mechanism  is  permanently  fastened  to  its 
shell  and  one  in  w'hich  there  is  a  detachable  mechanism.  The  one-piece 
switch  has  been  in  existence  since  the  beginning  of  electrical  control, 
and  has  been  improved  upon  from  time  to  time,  until  improvement 
had  to  take  a  long  jump  and  the  detachable-mechanism  switch  was 
evolved,  with  many  points  in  its  favor.  Granted  that  the  action  of  one 
mechanism  is  as  good  as  the  other  under  conditions  that  are  ideal  but 
which  seldom  obtain,  the  danger  of  damage  in  the  case  of  the  one-piece 
switch  is  often  detrimental  to  the  proper  action  of  the  mechanism.  A 
favorable  point  to  the  credit  of  the  one-piece  switch  is  its  first  cost.  The 
cost  to  install  each  switch  is  equal,  but  the  mechanism  of  the  one-piece 
switch  is  liable  to  injury  from  all  sources,  while  in  the  two-piece  switch 
the  shell  can  be  installed  independently  of  the  mechanism;  that  is,  the 
wires  can  be  permanently  connected  and  a  protecting  sheet  placed  in 


INTERIOR  WIRING  181 

the  shell.  The  mechanism  is  thus  not  liable  to  damage  by  plaster, 
paint,  water,  etc.,  present  in  both  new  and  old  buildings.  These  points 
are  very  often  overlooked,  while  they  are  very  important  to  switch  main- 
tenance. Complaints  are  very  often  lodged  against  a  non-operating 
switch,  and  in  most  cases  defective  operation  is  due  to  damage  caused 
by  plaster  getting  in  the  mechanism,  or  paint  causing  the  push  points 
to  stick,  or  water  or  dampness  causing  the  mechanism  to  rust.  These 
defects  are  likely  to  present  themselves  in  the  one-piece  switch,  because 
of  the  necessity  of  installing  the  switch  before  work  is  finished  in  the 
building,  so  as  to  complete  the  electrical  contract  on  time.  The  use  of 
the  two-piece  detachable-mechanism  switch  avoids  all  this  trouble,  be- 
cause of  the  installation  of  the  shell  only,  thus  saving  the  mechanism  from 
possible  damage  by  the  causes  given.  The  installation  of  the  mechanism 
calls  for  so  little  additional  labor  that  no  account  need  be  taken  of  it. 
The  replacing  of  a  switch  mechanism  that  has  given  out  by  hard  usage 
is  a  big  item  to  be  considered  when  making  the  initial  installation.  This 
may  seem  a  consideration  that  is  a  great  distance  off,  but  no  one  can 
judge  the  actual  operation  of  any  movable  mechanism,  as  can  be  seen 
by  the  guarantees  that  are  given,  which  seldom  run  over  two  years. 
The  installation  of  a  push  switch  is  often  made  with  the  idea  that  it  will 
last  as  long  as  the  building;  but  that  is  poor  judgment,  and  the  question 
of  replacement  should  be  taken  seriously.  The  replacement  of  the  one- 
piece  switch  means  labor  and  cost  equal  to  the  first  installation;  that  is, 
purchasing  a  complete  mechanism  and  shell,  disconnecting  wires  and 
switch  and  reconnecting  wires  and  switch,  with  the  possible  breaking 
of  wires  from  bending  and  handling,  thereby  shortening  them  and  re- 
quiring a  new  circuit  or  tap,  which  means  added  labor  and  expense. 
The  replacement  of  a  two-piece  switch  means  the  removal  of  the  plate, 
the  pulling  out  of  the  defective  mechanism,  the  insertion  of  the  new 
mechanism  and  the  replacement  of  the  plate,  all  of  which  is  done  in  less 
time  than  it  takes  to  write  about  it.  The  cost  for  replacement  is  in 
favor  of  the  two-piece,  detachable-mechanism  switch.  In  making  re- 
placements damage  done  to  the  surrounding  walls  has  to  be  considered, 
if  it  is  done  in  a  place  where  looks  count  for  something,  as  in  a  hotel, 
residence,  public  hall,  school,  office,  etc.  The  detachable-mechanism 
switch,  which  requires  little  labor  and  that  of  a  clean  nature,  thus  scores 
a  point.  Another  point  that  may  not  be  serious,  but  is  worthy  of  con- 
sideration, is  the  element  of  time  when  a  replacement  is  to  be  made,  say, 
in  a  guest's  room  in  a  hotel.  Nothing  need  be  said  regarding  which 
switch  is  more  advantageous  under  these  conditions.  The  installation 
of  a  one-piece  switch  under  similar  conditions  would  mean  that  the  elec- 
trician would  have  to  take  tools,  an  extension  lamp  cord  and  a  one-piece 
switch.  Arriving  at  the  room,  he  would  have  to  disconnect  the  defect- 


182 


HANDBOOK  OF  ELECTRICAL  METHODS 


ive  switch  and  reconnect  the  new  switch,  always  taking  the  precaution 
not  to  soil  the  walls.  There  are  a  number  of  instances  that  could  be 
cited  to  the  credit  of  the  two-piece  detachable-mechanism  switch. 

An  Electric  Iron  Installation  (By  George  Travert).— A  method  of 
supporting  the  conducting  cord  of  an  electrically  heated  iron  is  shown 
in  Fig.  1.  The  feature  of  the  arrangement  that  deserves  attention  is 
the  sliding  support  for  the  helical  spring  that  carries  the  cord.  The 
ordinary  method  of  supporting  the  cord  of  an  electric  iron  is  to  tie  it  to 
a  spring  which  is  attached  in  a  permanent  position  and  the  fact  that  the 
location  of  the  spring  is  fixed  hampers  the  movements  of  an  operator 
using  the  iron.  With  the  scheme  suggested  in  Fig.  1  the  spring  is  fas- 
tened with  an  "S"  hook  (see  Fig.  2)  to  a  porcelain  insulator  which 


Snap  Switch 
Indicator  Lamp 
Attachment  Plug 


FIG.    1  AND  2. AN  ELECTRIC  IRON  INSTALLATION  AND  METHOD  OF  SUPPORTING 

SPRING. 

» 

is  arranged  to  slide  back  and  forth  on  a  wire.  As  the  iron  is  pushed  to 
and  fro  the  porcelain  insulator  follows  its  movements  and,  as  the  spring 
will  stretch,  ironing  can  be  done  over  a  considerable  area.  It  should  be 
noted  that  at  all  times  the  conducting  cord  is  supported  well  out  of  the 
way  of  the  operator. 

Spiral  springs,  like  that  illustrated  in  Figs.  1  and  2,  are  usually 
furnished  by  the  manufacturers  with  all  sadirons,  so  that  the  only  addi- 
tional material  that  is  needed  to  make  such  an  installation  is  the  insulator, 
the  iron  wire  and  the  turnbuckle.  The  iron  wire,  Fig.  1,  is  made  up  in  a 
screw-eye,  inserted  in  the  wall  at  one  end  and  into  one  eye  of  a  small 
turnbuckle  at  the  other  end.  Such  a  turnbuckle  can  be  supplied  by 
any  first-class  hardware  house.  The  turnbuckle  provides  means  for 
keeping  the  wire  tight.  The  hook  end  of  the  turnbuckle  engages  with  a 
screw  eye  inserted  in  the  wall.  It  is  well  to  arrange  the  iron  wire  some- 
what to  the  rear  of  the  line  along  which  the  iron  will  be  used,  as  shown  in 
Fig.  3.  This  is  done  to  prevent  the  cord  from  striking  the  hand  of  the 
ironer. 

A  convenient  method  of  wiring'an  electric  iron  is  shown  in  Figs.  1 


INTERIOR  WIRING 


183 


and  4.  The  visible  components  of  the  circuit  are  shown  in  Fig.  1  and 
the  wiring  diagram  is  given  in  Fig.  4.  An  incandescent  lamp  of  small 
candle-power  is  connected  across  the  branch  circuit  to  the  iron  on  the 
iron  side  of  the  double-pole  switch.  So  long  as  the  switch  is  closed  and 
the  iron  connected  to  the  supply  source  the  lamp  will  glow  and  indicate 
the  fact  that  the  iron  is  "  alive."  This  device  not  only  tends  to  make 
the  operator  careful  in  his  use  of  energy,  but  it  assists  in  preventing 


Iron  Wire 

InsulatorYLamp 

~£_ 

Turnbuckle 

Normal  Path  of  Iron 

Ironing  Table 

Supply  Circuit 


Fuses 


Double-Pole 
Snap  Switch 

Inc.Indicator 
Lamp 

Receptacle 

Attachment 
Plug 

To  Iron 


FIGS.    3  AND  4. PLAN  VIEW  OF  INSTALLATION  AND  WIRING  DIAGRAM. 

the  fires  that  are  sometimes  caused  by  an  electric  iron  being  left  on  a 
wooden  ironing  board  while  connected  to  a  supply  source. 

Wiring  Buildings  with  Cinder-filled  Floors  (By  George  Hartley). — 
Occasionally  in  wiring  old  buildings  a  wireman  will  encounter  a  floor 
partly  filled  with  cinders  between  the  joists.  Floors  are  seldom  built 
in  this  way  now,  but  fifteen  or  twenty  years  ago  the  construction  was 
common  in  the  better  class  of  residences  and  business  buildings.  In 


Wood  Top  Floor 


Joist 


Lath  Plaster 

FIG.     1. WIRE  INSTALLED  BENEATH  CINDER-FILLED  FLOORS. 

running  circuits  beneath  such  a  floor  the  wireman  can  take  out  some  of 
the  cinders  after  removing  the  floor  boards  parallel  to  the  run.  Only 
enough  cinders  should  be  taken  out  between  each  pair  of  joists  to  expose 
a  complete  " bridge"  board  so  that  it  can  be  pried  out.  The  bridge 
board  out  of  the  way,  the  holes  for  the  tubes,  or  for  flexible  conduit  if 
such  is  used,  are  bored  below  the  cleats  with  a  long  bit.  The  latter 

13 


184 


HANDBOOK  OF  ELECTRICAL  METHODS 


type  is  necessary  because  one  of  ordinary  length  cannot  be  used,  owing 
to  insufficient  working  room.  If  a  long  bit  is  not  at  hand,  one  can  be 
made  by  having  a  blacksmith  weld  a  shank  of  the  necessary  length, 
possibly  30  in.,  to  an  ordinary  carpenter's  bit.  Fig.  2  illustrates  the 
conditions  that  prevail  while  the  joists  are  being  bored.  After  the 
procelain  tubes  have  been  inserted  and  the  wire  threaded  through 
them,  or  after  the  flexible  conduit  has  been  run  through  the  holes,  the 
bridge  pieces  may  be  nailed  in  place.  The  cinders  may  then  be  scraped 
back  and  the  top  floor  boards  relaid.  Fig.  1  on  page  180  illustrates  a 
sectional  view  of  a  finished  job. 


\^--^~  Center  Line  of  Bit 

Cinder  Filling 
Removed 

|               "  I 

/ 

One  Bridge 
\^             Board^ 
~"-\     RcmovedX. 

5*5 

7 

^ 

F= 

I                                    ""\                    1 

|                                                                                                                                                                         | 

J 

*  Holes  for  Tubes 

>- 

1 

Uith                                        Plaster 

FIG.    2. — BORING  HOLES  THROUGH  JOISTS. 

Home-made  Chandelier  Hooks  and  Loops  (By  E.  B.  Watson).— 
Chandelier  loops  and  hooks  are  often  used  in  connection  with  conduit 
wiring  installations.  Applications  are  shown  in  Figs.  1  and  2  on  page 
182.  Fig.  1  represents  an  arc  lamp  suspended  at  the  middle  of  a 
bay,  in  a  building  of  wooden  mill  construction,  by  a  chandelier  loop  and 
hook.  From  the  loop  a  chain  is  carried  to  the  roof  above  and  secured  in 
a  screw-eye  turning  into  the  roof  timbers.  Through  this  arrangement 
the  stress,  due  to  the  weight  of  the  lamp,  is  taken  almost  wholly  by  the 
chain  and  there  is  practically  no  tendency  for  the  conduit  to  break,  in 
the  threads,  where  it  turns  into  the  conduit  tee.  If  a  chain  or  some 
auxiliary  support  is  not  used  1/2-in.  conduit  will  not  support,  without 
excessive  deflection,  an  arc  lamp  at  the  center  of  a  20-ft.  bay.  The  lamp 
hangs  on  a  chandelier  hook  turned  into  the  bottom  outlet  of  the  conduit. 

Fig.  2  illustrates  a  method,  often  utilized,  for  supporting  a  tungsten 
lamp  fixture  at  some  point  between  trusses.  The  example  is  taken  from 
an  installation  in  a  steel  factory  building.  The  main  conduit  is  clamped, 
with  U-bolts,  against  the  upper  edges  of  the  two  angles  forming  the  bot- 
tom chords  of  the  roof  trusses.  Two  chains  are  necessary  here.  Each 
chain  is  made  fast,  at  its  upper  end,  to  one  of  the  truss  members  near  the 
roof.  It  would  not  be  practicable  to  use  only  one  vertical  chain,  because 
the  roof  is  a  concrete  slab  to  which  attachment  would  be  difficult.  It  is 
cheaper  and  better  to  use  two  chains  than  to  drill  and  plug  the  concrete 
roof  in  order  to  effect  an  attachment. 


INTERIOR  WIRING 


185 


In  both  of  the  cases  cited  (Figs.  1  and  2)  the  chandelier  loop  is  of 
the  ordinary  commercial  pattern,  which  can  usually  be  obtained  at  any 
plumbing  or  electrical  supply  house.  It  will  be  usually  cheaper  to  buy 
chandelier  loops  and  hooks  ready  made  than  to  make  them.  If  it  is  not 
practicable  to  buy  them,  or  if  some  are  needed  immediately  and  there  is 
not  enough  time  to  send  to  the  dealer,  they  may  be  made  as  suggested  in 
Figs.  3  and  4. 

Ijj    Supporting 
Chandelier          M —  Chain 
Loop 


FIG.    1. CHANDELIER  LOOP  AND  HOOK 

SUPPORTING  ARC  LAMPS. 


FIG.    2. TUNGSTEN  FIXTURE  SUP- 
PORTED BY  CHANDELIER  LOOP. 


In  the  method  shown  in  Fig.  3,  an  ordinary  commercial  pipe  cap  is 
drilled  and  tapped,  and  a  piece  of  wrought-iron  rod,  say  of  a  diameter  of 
1/4  in.  is  threaded  on  one  end  and  has  a  ring  formed  at  its  other  end. 
Whether  the  ring  is  left  open  or  closed  depends  on  whether  the  resulting 
appliance  is  to  be  a  loop  or  a  hook.  The  threaded  end  of  the  loop  or  hook 


Standard  Pipe  Cap 

FIG.    3. CHANDELIER  LOOP 

MADE  FROM  PIPE  CAP. 


Standard  Pipe  Plug 

FIG.    4. CHANDELIER  LOOP 

MADE  FROM  PIPE  PLUG. 


is  turned  into  the  hole  tapped  in  the  cap  and  the  device  is  complete. 
To  prevent  any  possibility  of  the  loop  turning  out  of  the  hole  it  is  a  good 
plan  to  " bead-over"  its  end  on  the  inside  of  the  pipe  cap.  The  wrought- 
iron  rod  shown  in  Fig.  3  is  so  bent  as  to  form  a  hook  rather  than  a  loop. 
A  " home-made"  loop  is  illustrated  in  Fig.  4.  In  this,  a  pipe  plug,  a 


186  HANDBOOK  OF  ELECTRICAL  METHODS 

readily  obtainable  fitting,  is  drilled  and  tapped  to  receive  the  threaded 
end  of  the  loop.  The  construction  outlined  in  Fig.  3  is  neater  than  that 
of  Fig.  4,  but  usually  either  is  installed  where  it  cannot  be  seen,  so  ap- 
pearance is  of  little  consequence.  The  plug  loop  (Fig.  4)  can  be  turned 
directly  into  a  conduit  fitting  while  an  additional  nipple  is  required  where 
the  cap  loop  (Fig.  3)  is  used.  Because  of  this  the  plug  construction  is 
usually  preferred. 

Simplifying  Concealed  Conduit  Work  (By  T.  W.  Poppe). — It  seems 
strange  that  after  several  years'  use  of  rigid  conduit  in  a  progressive  and 
inventive  country  the  bending  of  conduit  for  concealed  work  is  still 
adhered  to.  Special  fittings  are  manufactured  which  greatly  simplify  the 

Conduit  \  ^  Conduit 


Concrete 
Arch 

FIG.    1. CORRECT  INSTALLATION  OF  BENT  CONDUIT. 

installation  of  exposed  conduit.  But  no  genius  has  turned  his  talent 
toward  simplifying  the  installation  of  concealed  conduit.  No  doubt  a 
great  saving  of  time  would  be  affected  if  a  fitting  could  be  manufactured 
to  obviate  the  necessity  of  bending  the  several  conduits  which  go  through 
the  concrete  floor  to  the  lamp  outlet  on  the  ceiling  below. 

For  example,  when  installing  conduit  in  a  fireproof  building  where  the 
arches  or  bays  are  made  of  concrete,  the  plan  now  followed  is  to  run  the 
conduit  from  outlet  to  outlet  while  the  concrete  mixture  is  still  soft.  This 
means  that  one  conduit  must  enter  the  outlet  and  one  must  leave  it. 

Points  Liable 
to  Damage  Conduits 


FIG.    2. IMPROPER  POSITION  OF  CONDUIT  AND  BENDS. 

As  the  wooden  forms  which  support  the  concrete  mixture  must  necessarily 
remain  in  position  until  the  mixture  has  hardened,  a  hole  must  be  cut 
through  the  wooden  form  at  the  position  where  the  outlet  is  to  be  located 
and  the  bent  ends  of  the  conduits  placed  therein.  It  is  manifestly 
impossible  to  place  the  outlet  box  in  position  at 'this  time  owing  to  the 
wooden  form.  The  laying  of  the  conduit  while  the  concrete  filling  is 
being  placed  saves  much  time,  as  it  is  a  laborious  process  to  cut  through 
the  concrete  after  it  has  hardened.  With  the  present  system  of  bending 
conduits  it  is  also  a  bad  method  because  the  wheeling  of  barrows  and  the 
traveling  of  laborers  and  mechanics  over  the  loose  conduits  throw  them 


INTERIOR  WIRING  187 

out  of  position  and  produce  the  condition  shown  in  Fig.  2.  Where  such  a 
condition  exists  it  is  an  expensive  job  to  cut  the  hardened  concrete 
around  the  displaced  conduits  and  bend  them  into  a  position  where  an 
outlet  box  can  be  attached  to  them.  It  also  invariably  means  that  the 
outlet  is  moved  from  its  correct  position  and  the  symmetry  of  the  entire 
work  destroyed. 

The  bending  of  conduit  is  also  a  laborious,  time-consuming  process, 
as  the  bends  must  be  made  about  5  in.  from  the  end  of  the  conduit 
because  the  concrete  arches  are  seldom  made  more  than  4  in.  thick.  If 
a  larger  bend  is  made  the  conduit  projects  upward  and  is  more  liable  to 
damage  from  wheelbarrows  and  other  causes.  Figs.  1  and  2  show  a 
correct  and  incorrect  installation  of  bent  conduits. 

In  exposed  work  the  bending  of  conduit  by  the  use  of  fittings  on  the 
market  can  be  wholly  eliminated,  if  desired,  and  the  work  made  as 
satisfactory  as  by  the  older  method  of  bending  the  conduit.  The  draw- 
ing-in  of  the  wire  becomes  a  simple  task  also..  Fig.  3  shows  a  fitting  the 

Coupling 

Inside  Dia. 


FIG.    3.  -  FITTING  DESIGNED  TO  AVOID  BENDING  OF  CONDUITS. 

use  of  which  will  obviate  the  bending  of  conduits  and  which  also  provides 
a  strong,  substantial  fixture  support.  The  fitting,  which  can  be  made 
of  malleable  iron  to  withstand  rough  handling,  is  equal  in  external 
diameter  to  the  standard  3/4-in.  conduit.  At  each  horizontal  end  the 
inside  diameter  is  enlarged  to  13/16  in.  to  a  depth  of  1  1/4  in.  This 
allows  the  standard  1/2-in.  conduit  to  slip  into  it.  On  each  horizontal 
end  a  3/4-in.  pipe  thread  is  cut  to  a  point  1  1/2-in.  from  the  end.  Each 
end  is  then  cut  its  entire  threaded  length,  the  cut  being  1/16  in.  wide. 
The  thread  will  allow  a  standard  coupling  to  be  screwed  upon  it.  When 
the  coupling  is  screwed  on  it  compresses  the  sections  of  the  thread  divided 
by  the  one-sixteenth  cut  and  grips  the  1/2-in.  conduit,  which  is  pushed 
into  the  fitting.  After  the  conduit  is  pushed  into  the  fitting  and 
before  the  coupling  is  screwed  on,  an  application  of  white  lead  or  other 
water-resisting  compound  should  be  made  to  the  thread.  When  the 
coupling  is  screwed  on  the  thread  it  forces  the  compound  into  the  crevice 
formed  by  the  cut  and  makes  a  waterproof  joint  as  required  by  the 
Underwriters. 

The  use  of  this  fitting  not  only  obviates  the  bending  of  the  conduits, 
but  it  also  saves  the  cutting  of  many  threads.  Under  the  present  system 
the  conduits  are  bent  as  desired,  then  measured  and  taken  to  a  vise, 


188 


HANDBOOK  OF  ELECTRICAL  METHODS 


where  they  are  cut  and  threaded.  With  this  fitting  the  conduit  can  be 
cut  where  the  fitting  is  being  installed  and  as  no  thread  is  required  the 
conduit  can  be  pushed  into  the  fitting,  while  lead  is  applied  and  the  coup- 
ling tightened.  A  1  1/4-in.  hole  can  be  bored  through  the  wooden  form 
sustaining  the  concrete  mixture  and  the  vertical  portion  of  the  fitting 
placed  therein.  A  washer  can  be  placed  over  it  and  by  screwing  a  lock 


Fitting 


Conduit' 


FIG.    4. FITTING  IN  POSITION  IN  CONDUIT. 

nut  on  the  vertical  end,  which  is  also  threaded,  the  fitting  and  conduit 
can  be  firmly  clamped  to  the  arch.     Fig.  4  shows  a  fitting  in  place. 

When  the  wooden  forms  supporting  the  concrete  are  removed  the 
lock  nut  and  washer  can  be  removed  and  an  outlet  box  placed  in  position 
by  slipping  it  over  the  fitting,  using  the  center  of  the  box  and  forcing  it 

Fitting 


Outlet  Box 
Plaster  Line 


Locknut 


FIG.    5. FITTING  AND  OUTLET  BOX  IN  PLACE. 

against  the  concrete  by  means  of  a  lock  nut.  After  the  plastering  is 
finished  the  rigidity  of  the  box  is  greater  because  of  the  hardening  of 
plaster  surrounding  the  box.  Fig.  5  shows  a  fitting  and  outlet  box  in 
position. 

Conduit  Systems  in  Concrete  Buildings  (By  J.  P.  Morrissey). — Loss 
by  experience  in  conduit  work  made  the  contractors  cast  about  for  some 


Concrete 


/Wood  Block 


Wood  Form 


^^plspl 


FIG.    1. PROVISION  IN  CONCRETE  FLOOR  FOR  OUTLET. 

method  of  avoiding  expensive  and  laborious  punching,  and  finally  a 
round  wood  block  especially  made  to  suit  the  construction  and  location 
on  the  wood  forms  at  the  location  of  the  outlet  was  devised,  as  shown  in 
Fig.  1.  These  blocks  were  made  with  a  small  diameter  at  the  bottom  of 
approximately  the  size  of  an  outlet  box  and  tapering  to  a  larger  diameter 
at  the  top,  so  as  to  prevent  them  coming  out  when  the  concrete  forms 


INTERIOR  WIRING 


189 


were  removed.  The  blocks  are  of  a  depth  to  suit  the  thickness  of  the 
concrete  slab  construction.  The  concrete  is  poured  after  the  block  is 
properly  set  and  fastened,  and  the  opening  in  the  concrete  slab  after  it 
has  set  and  the  block  has  been  removed  leaves  easy  access  for  the  installa- 


Finished  Floor 


Cinder  Fill        Outlet  Box 


Conduit 


Concrete 

\ 


£.-Jp-:;: 

.•.'•:  •'•LV'.V 

i^^£ti 

* 

i 

^-.  Finished 
Plaster 

^ 
Collar 

• 

:•&;.,'.•'/»-". 

..•/.•^/.•,<5: 

FIG.    2. METHOD  OF  BRINGING  OUTLET  TO  CEILING  LEVEL. 

tion  of  the  outlet  boxes  and  conduit.     These  blocks,  being  special,  are 
expensive;  therefore,  much  care  is  exercised  in  their  removal. 

After  the  blocks  are  removed  one  method  of  installing  the  conduit 
and  outlets  is  to  bring  the  outlet  down  flush  with  the  ceiling,  thereby 
necessitating  sharp  and  small  bends,  depending  on  the  allowable  thickness 


Finished  Floor 


Cinder  Fill      Conduit 


Concrete 


1"    "•"  •:  

/-••?;'•'•:-?:  --.••-^'. 
/.  £  -•-•.-.>:.•;.  'A.-.-: 

«$$$ 

V-'feM^jK-V.^'1  ^r^?fe^\ni'  ?^M^ 

W 

?f 

'c'^-T'-vsi-^-----^'"^^ 
;l:-:A'^:->>Vft.^'-?.v>^:-:^'( 

>  :V-  •*-'?/ 
;',:^-.V-\V- 

•'.i^fe^' 

Finished                   Outlet  Box 
~~  Plaster 

1 

FIG.    3. METHOD  OF  INSTALLING  CONDUIT  IN  CONCRETE  FLOOR. 

of  construction  to  the  finished  floor,  so  as  to  prevent  its  being  exposed,  as 
shown  in  Fig.  2.  Where  conditions  will  not  permit  such  installation 
the  outlet  box  is  placed  over  the  opening  left  by  the  removal  of  the 
block  and  the  conduits  are  installed  running  into  the  side  of  the  outlet 
box,  properly  and  securely  fastened.  A  sheet- iron  collar  is  then  made 


finished  Floor       Cinder  Fill 


Conduit 


Cone 


FIG.    4. — BOX  AND  CONDUIT  EMBEDDED  IN  CONCRETE  FLOOR. 

up  of  the  proper  depth  and  bolted  to  the  outlet  box,  thereby  making 
a  box  to  the  level  of  the  finished  ceiling,  as  shown  in  Fig.  2.  These 
methods  do  not  prove  very  satisfactory,  and  the  conduit  and  outlet 
boxes  are  now  installed  on  the  forms  before  the  concrete  is  poured.  This 
gives  the  most  satisfactory  results  and  adds  greatly  to  the  rapid  comple- 
tion of  this  class  of  building.  The  wood/orms  are  set  with  the  reinforcing 


190  HANDBOOK  OF  ELECTRICAL  METHODS 

wire  netting,  and  upon  these  the  outlet  boxes  with  one  length  of  conduit 
are  located,  as  shown  in  Fig.  4.  The  location  for  the  outlet  box  is  found 
and  a  nail  is  driven  into  the  wood  form  at  the  exact  center.  The  outlet 
box  is  made  up  with  the  fixture  hanger  securely  and  properly  attached, 
and  the  center  of  the  hanger  is  set  over  the  nail  at  the  outlet  location. 
The  box  is  then  fastened  to  the  form  with  wire  nails. 

The  outlet  boxes  are  deep  enough  to  permit  the  conduit  to  enter  on 
the  sides.  The  conduit  rests  on  top  of  the  netting.  In  a  great  many 
instances  the  conduit  actually  is  a  reinforcement  to  the  concrete  con- 
struction and  can  be  completed  back  to  the  distribution  box  location  and 
be  turned  up  or  down  at  switch  locations  as  conditions  necessitate.  This 
gets  the  conduit  located  out  of  harm's  way  and  does  not  permit  it  to  be 
trampled  on  or  run  over  with  wheelbarrows. 

Galvanized  iron  and  steel  conduit  have  been  used  almost  exclusively, 
and  have  proved  satisfactory  as  far  as  results  are  concerned.  The  free 
use  of  white  lead  on  all  joints  is  a  point  insisted  upon  for  the  best  results. 
The  boxes  used  are  also  galvanized  to  withstand  the  corroding  action  of 
the  concrete  mixture.  The  wire  nails  that  are  used  for  fastening  are  so 
eaten  by  the  concrete  mixture  that  it  is  not  a  difficult  job  to  remove  them 
before  pulling  in  the  wire.  Placing  the  outlet  box  flush  on  the  forms 
brings  it  almost  to  the  finish  of  the  ceiling,  which  is  very  rarely  thicker 
than  the  face  ring  which  is  added  to  the  outlet  box  after  the  forms  are 
removed.  The  fixture  hangers,  which  have  proved  very  satisfactory, 
are  made  up  of  a  T  fitting,  into  which  a  piece  of  conduit  not  less  than  15 
in.  long  has  been  inserted  and  a  threaded  stem  installed,  locking  itself 
against  the  cross  head  and  then  being  bolted  to  prevent  turning.  The 
stem  is  made  long  enough  to  come  half  way  down  in  the  outlet  box, 
thereby  leaving  space  for  the  insulating  joint.  Another  fixture  hanger 
that  has  given  satisfaction  when  properly  installed  is  made  up  with  a 
"  Thomas  &  Betts"  loop  head.  A  length  of  conduit  is  installed  in  the 
loop  and  a  stem  is  screwed  into  the  bottom  of  the  loop  and  wedged  against 
the  conduit.  A  small  nail  is  then  driven  into  an  opening  for  that  purpose, 
which  spoils  the  threads  of  the  stem  and  prevents  it  from  turning.  The 
McKnight  hanger  has  also  given  satisfaction,  but  requires  care  in  in- 
stallation. This  hanger  is  all  made  up  ready  for  installation,  and  it  is 
only  necessary  to  lock  it  into  an  outlet  box  with  lock  nuts,  one  on  the 
inside  and  one  on  the  outside,  and  then  let  it  stand  in  a  vertical  position 
until  the  concrete  is  poured  around  it.  The  holding  bands  are  then 
offset  and  fastened  with  nails  at  the  points  on  the  bands  made  for  that 
purpose. 

There  have  been  instances  where,  because  of  the  conduit  being 
embedded  in  the  concrete,  spikes  have  been  driven  through  the  conduit 
to  fasten  sleepers  for  flooring,  but  the  cases  are  very  rare  because  the 


INTERIOR  WIRING 


191 


more  modern  floors  are  of  cement  finish  that  do  not  require  any  spike 
driving.  There  are  also  instances  where  concrete  has  leaked  in  to  con- 
duits at  joints,  but  this  is  faulty  construction  that  might  occur  in  any 
concrete  construction.  These  are  the  only  faults  that  have  presented 
themselves. 

Mitering  Metal  Molding  (By  G.  A.  Harris). — The  following  article 
describes  a  method  of  forming  elbows  and  turns  in  metal  wiring  without 

90°For  a  Right  Angle  Elbow 


Screw 

Hole 


Base 


For  a  Eight  Angle  Elbow 


Capping 
Miter  Cuts 

FIG.    1. — MITERED  TURN 
Countersunk  Holes  Bend  on  the  Line 


b 

X                         © 

J^ 

^-^                                ^ 

,Cut-out  with  Hack  Saw 


Miter  Inside  Bend  Miter  Outside  Bend 

FIGS.  2,  3  AND  4. MITERED  ELBOW 


Base 


the  insertion  of  conducting  pieces  to  maintain  the  electrical  continuity 
of  the  molding.  Fig.  1  illustrates  how  a  piece  of  base  is  cut  to  form  a 
right-angle  elbow,  leaving  a  portion  of  one  edge  intact  to  afford  conduc- 
tivity. After  cutting  the  two  ends  of  the  base  are  bent  together  until 
the  two  cut  faces  abut.  The  two  end  lengths  will  then  be  at  right  angles 


192 


HANDBOOK  OF  ELECTRICAL  METHODS 


to  one  another.  Cappings  for  such  a  90-deg.  elbow  are  mitered,  as  shown 
in  the  bottom  of  Fig.  1,  and  are  snapped  over  the  base  after  it  has  been 
erected.  The  base  for  an  internal  bend  may  be  cut  for  a  90-deg.  turn,  as 
shown  in  Fig.  2.  In  Fig.  3A  the  base,  which  has  been  cut  as  outlined  in 
Fig.  2,  is  shown  in  position  in  the  corner,  ready  to  receive  the  capping, 
and  at  B  it  is  shown  with  the  capping  in  position.  It  will  be  noticed 
that  it  is  not  necessary  to  miter  the  capping,  as  it  completely  incloses  the 
slot  in  the  base  if  pushed  into  the  corner  as  suggested  at  Fig.  3£.  For 
an  external  bend  the  base  is  cut  with  a  hack-saw,  as  shown  at  A  (Fig.  4), 
and  is  then  bent  and  secured  on  the  corner  as  outlined  at  B.  The  cap- 
ping for  an  external  bend  should  be  mitered  as  detailed  at  C.  When 
this  is  done  there  may  be  a  small  hole  just  at  the  apex  of  the  angle  in- 
cluded within  the  molding,  as  shown  in  the  illustration,  but  this  is  of  no 
consequence.  In  construction  with  conducting  pieces,  two  screws  or 
bolts  are  required  at  each  turn  or  elbow  to  maintain  the  electrical  con- 
tinuity of  the  run.  Where  molding  (as  herein  outlined)  is  electrically 
continuous,  it  can  often  be  wrell  supported  by  screws  inserted  through 
the  holes  punched  in  the  base  by  its  makers.  Where  this  is  done  the 
extra  labor  of  drilling  additional  screw  holes  and  of  driving  the  extra 
screws  is  avoided. 

Erection  of  Metal  Molding  (By  A.  G.  Tonstead). — Right-angle  turns 
in  metal  molding  runs  are  ordinarily  made  with  metal-molding  elbow 


Metal 
Elbow    Capping 


Metal 
Moulding 


Metal 


FIG.    1. TURN  MADE  WITH  ELBOW.          FIG.    2. TURN  MADE  BY  MITERING. 


FIG.   3. METHOD  OF  LAY- 
ING OUT  A  MITER  CUT. 


Metal. 

Metal         Capplng 
Internal 
Bend 


^J    Capping 

*-  Metal 
Base 


FIG.   4. ELBOW  FORMED 

WITH  FITTINGS. 


FIG.    5. ELBOW  FORMED 

BY   MITERING. 


INTERIOR  WIRING 


193 


fittings,  as  shown  in  Fig.  1.  A  more  sightly  turn  can  be  made,  without 
elbow  fittings,  as  suggested  in  Fig.  2,  by  mitering  the  capping  and  base 
in  much  the  same  way  as  wooden  molding  would  be  mitered.  The 
miter  is  cut  with  a  hack-saw.  A  miter-box  can  be  used  to  guide  the  saw 
or  the  cut  can  be  made  quite  satisfactorily  by  laying  off  a  distance,  W, 
Fig.  3,  equal  to  the  width  of  the  capping  or  brace,  as  the  case  may  be, 


Conducting 
Piece 


ritove 
13olt 


Metal 
Base  V 


Screw 
Stove 

jV'      Metal     I 
V           Base     \ 

> 

--~A                   1 

Bolt 

4; 

Toggle 

-Bolt 

FIG.    6. APPLICATION  OF  CONDUCTING  PIECES. 

along  its  side  and  indicating  it  with  a  pencil  mark.  The  saw  cut  should 
be  made  connecting  the  corner  of  the  molding  with  the  pencil  mark.  After 
a  wireman  has  done  a  little  mitering  he  can  judge,  with  his  eye,  the  angle 
that  the  cut  should  take  and  can  dispense  with  the  miter-box  and  the 
marking.  Metal  molding  is  flexible  enough  to  let  it  be  bent  to  meet  at 
mitered  corners  if  the  cutting  is  a  little  inaccurate. 


Formed 


FIG.   7. TOGGLE  BOLT  FOR  METAL 

MOLDING. 


FIG.    8. TOGGLE  BOLT 

BEING  INSERTED. 


Elbows  can  be  formed  in  somewhat  the  same  way  that  turns  are 
made.  Fig.  4  shows  the  usual  method  where  fittings  are  used  and  Fig. 
5  shows  how  it  can  be  done  by  mitering.  It  is  required  by  the  National 
Electrical  Code  that  metal  molding  be  so  installed  that  adjacent  lengths 
of  molding  will  be  mechanically  and  electrically  secured  at  all  points. 
Where  work  is  subject  to  Underwriters'  inspection,  connecting  pieces, 
cut  from  scraps  of  molding,  can  be  inserted  as  outlined  in  Fig.  6,  to  join 


194 


HANDBOOK  OF  ELECTRICAL  METHODS 


adjacent  lengths  electrically  and  mechanically.  Where  molding  is  being 
erected  on  a  wooden  surface  flathead  wood  screws  can  be  used  for  support- 
ing it  and  for  effecting  the  connection  between  the  conducting  piece  and 
the  base  pieces.  (It  is  required  by  the  code  that  the  heads  of  any  bolts 
or  nuts  must  lie  flush  with  the  interior  face  of  the  base,  after  they  have 
been  inserted.)  On  concrete  surface  screws,  turning  into  expansion 
anchors,  or  stove  bolts  can  be  used  on  tile  fireproofing.  Where  stove 
bolts  are  utilized  small  cavities  must  be  chipped  in  the  supporting  surface 
to  accommodate  the  nuts,  but  it  is  often  more  convenient  to  chip  these 
holes  than  to  drill  for  an  expansion  anchor  or  a  toggle  bolt. 

Toggle  bolts,  of  the  form  detailed  in  Fig.  7,  are  well  adapted  for 
fastening  metal  molding  to  tile  fireproofing.  The  bolt  itself  is  threaded 
its  entire  length.  The  toggle  is  pivoted  eccentrically  and  the  long  end 
tends  to  lie  close  to  the  bolt  while  it  is  being  inserted,  as  shown  in  Fig.  8. 
After  the  toggle  is  through  the  hole  it  can  be  thrown  into  a  horizontal 
position  by  twirling  the  bolt  or  by  jiggling  it  up  and  down.  Two  sizes 
of  toggle  bolts  are  used  for  supporting  molding.  The  1/4-in.  size  shown 
is  very  satisfactory.  The  other  size,  3/16-in.,  is  a  trifle  light  for  all- 
around  work.  A  length  of  4  in.,  as  suggested  in  Fig.  7,  is  about  right 
for  the  average  condition. 

All  holes  drilled  for  supporting  screws  or  bolts  in  metal  molding  base 
should  be  countersunk.  A  special  bit  for  this  work,  having  a  square 
shank  which  fits  the  ordinary  brace,  is  available.  It  is  a  combination 
drill  and  countersink,  in  that  it  drills  and  countersinks  at  one  operation, 
and  is  a  convenient  tool.  The  base  is  usually  drilled  and  countersunk 
by  its  manufacturers  to  accommodate  No.  8  wood  screws.  These  have  a 
diameter  of  a  trifle  over  5/32  in.,  about  No.  6  B.  &  S.  gage. 

Wiring  in  Metal  Molding  (By  M.  C.  Rice). — Wiring  in  approved  metal 
molding  can  be  used  for  exposed  work  for  circuits  where  the  difference  of 
potential  is  not  over  300  volts  and  where  the  load  does  not  exceed  660  volts. 


Conductors 


Base 


*c 


v Capping 


Capping 


Section 


FIG.    1. DIMENSIONS  OF  NATIONAL  METAL  MOLDING. 


INTERIOR  WIRING 


195 


Metal  molding  must  be  continuous  from  outlet  to  outlet,  to  junction  boxes 
or  to  approved  fittings  designed  especially  for  use  with  metal  molding. 
All  outlets  must  be  provided  with  approved  terminal  fittings,  which  will 
protect  the  insulation  of  conductors  from  abrasion,  unless  such  protec- 


External  Elbow 
Porcelain  Rosette  .    Internal  Elbo 


Section  on  Line    A-B 

FIG.    2. APPLICATION  OF  METAL  MOLDING  AND  FITTINGS. 

tion  is  afforded  by  the  construction  of  the  boxes  or  fittings.     Metal  mold- 
ing should  not  be  used  in  damp  places. 

Single-braid,  rubber-insulated  wire  is  approved.  In  all  cases  wires 
must  be  laid  in  and  not  fished.  There  is  sufficient  space  in  the  channel 
molding  shown  in  Fig.  1  for  four  No.  14  single-braid,  rubber-insulated 


Capping 


\ 
Conductors 


FIG.    3. LUTZ  METAL  MOLDING. 


wires.  It  is  often  necessary  to  insert  this  number  of  wires  at  double- 
pole  switch  loops,  etc.  The  two  or  more  wires  of  an  alternating-current 
circuit  must  be  in  the  same  molding,  and  those  of  a  direct-current  cir- 
cuit should  be  so  that  if  a  change  is  made  to  alternating-current  recon- 
struction will  not  be  necessary. 

One  common  form  of  metal  molding  consists  of  channel  capping  that 


196  HANDBOOK  OF  ELECTRICAL  METHODS 

snaps  over  a  channel  base.  The  principal  dimensions  are  given  in  Fig. 
1.  It  is  furnished  in  lengths  of  8.5  ft.  and  is  "sherardized."  Either 
water  or  oil  paint  adheres  well  to  it.  Because  of  the  small  space  that  it 
occupies  it  can  be  used  to  advantage  on  steel  ceilings,  in  show  windows, 
in  showcases  and  in  other  locations  where  appearance  is  a  factor  and 
where  safety  is  essential.  The  application  of  molding  of  this  form  is 
illustrated  in  Fig.  2 — an  imaginary  lay-out  shown  to  indicate  how  the 
material  may  be  used. 

Metal  molding  of  another  design  consists  of  a  channel-shaped  base 
and  a  strip  of  sheet  metal  that  slips  in,  as  illustrated  in  Fig.  3,  which 
constitutes  the  capping.  It  is  electro-galvanized  and  is  furnished  in 
10-ft.  lengths.  Capping  can  be  removed  at  either  end  or  at  any  other 
point  desired  by  making  two  hack-saw  cuts  with  a  fine-tooth  (tubing) 
saw  through  the  flanges  of  the  base  and  slightly  opening  the  cut  portion 
to  release  the  ends  of  the  capping.  It  is  recommended  that  in  making 
installations  these  hack-saw  cuts  be  made  at  intervals  to  permit  the  future 
removal  of  the  capping.  Fittings  for  molding  of  this  type  are  made  some- 
what similar  to  those  illustrated  in  Fig.  2.  All  fittings  are  arranged  to 
insure  electrical  conductivity  throughout  the  molding  installation. 

Where  metal  molding  passes  through  floors  it  should  be  carried 
through  an  iron  pipe  extending  from  the  ceiling  below  to  a  point  5  ft. 
above  the  floor,  which  will  serve  as  an  additional  mechanical  protection 
and  exclude  moisture.  In  residences,  office  buildings  and  similar  loca- 
tions where  appearance  is  an  essential  feature  and  where  the  mechanical 
strength  of  the  molding  itself  is  adequate  the  iron  pipe  can  extend  from 
the  ceiling  below  to  a  point  3  in.  above  the  floor. 

Metal  molding  must  be  grounded  permanently  and  effectively  and  so 
installed  that  adjacent  lengths  of  molding  will  be  mechanically  and 
electrically  secured  at  all  points.  It  is  essential  that  the  metal  of  such 
systems  be  joined  so  as  to  afford  electric  conductivity  sufficient  to  allow 
the  largest  fuse  in  the  circuit  to  operate  before  a  dangerous  rise  of  tem- 
perature in  the  system  can  occur.  Moldings  and  gas  pipes  must  be 
securely  fastened  in  metal  outlet  boxes  so  as  to  secure  good  electrical 
connection.  Where  boxes  used  for  centers  of  distribution  do  not  afford 
a  good  electrical  connection  the  metal  molding  must  be  joined  around  them 
by  suitable  bond  wires.  Where  sections  are  installed  without  being 
fastened  to  the  metal  structure  of  the  building  or  grounded  metal  piping 
they  must  be  bonded  together  or  joined  to  a  permanent  and  effective 
ground  connection. 

The  metal-molding  manufacturers  provide  fittings  suitable  for  joining 
adjacent  lengths  of  backing  together  and  ground  clamps  (Fig.  3)  for 
grounding.  Lapping  the  capping  from  one  length  to  the  adjacent  one 
constitutes  an  electrical  connection.  Ground  wires  must  be  at  least 


INTERIOR  WIRING 


197 


No.  10  B.  &  S.  gage,  although  smaller  wire  is  permitted  in  some  munici- 
palities. 

In  installing  mevtal  moldings  the  following  suggestions  will  be  found  of 
value.  Reasonable  care  should  be  exercised  in  separating  the  backing 
and  capping  preparatory  to  installation.  As  the  quickest,  most  satis- 
factory method,  hooking  one  of  the  punched  holes  in  the  backing  over  a 
convenient  nail  or  screw  and  drawing  the  capping  off  is  recommended. 
Except  in  cases  where  the  backing  of  the  molding  passes  through,  under 
the  fittings  and  is  not  cut,  backing  and  capping  should  be  cut  before 
being  separated  in  all  cases.  Because  of  the  light  stock,  hack-saw  blades 
having  fine  teeth  and  commonly  known  as  "  tube  saws  "  should  be  used  for 
cutting.  Some  construction  men  recommended  marking  deeply  with  a 


Ground  Wire 
Soldered  to  Clarnps 


Gas  and  Water  Pipe 

Ebctncal  World 


FIG.    4. — GROUNDING  METAL  MOLDING. 


file  and  breaking.  The  molding  is  readily  bent  and,  with  reasonable 
care,  may  be  worked  to  any  radius  down  to  one  of  4  1/2  in.  Bends  must 
be  made  in  all  cases  before  backing  and  capping  are  separated. 

The  backing  is  punched  and  countersunk  every  24  in.  for  the  support- 
ing screws  or  bolts.  The  support  so  afforded  will  usually  be  found  more 
than  ample,  but  further  support  may  be  secured  either  through  additional 
punching  with  a  special  punch  or  by  using  a  metal  molding  clamp. 
Fig.  8  of  A.  G.  Tonstead's  article  on  Erection  of  Metal  Moulding,  page 
193,  shows  a  toggle-bolt  support  as  employed  for  metal  molding.  When 
the  metal  molding  is  installed  on  uneven  surfaces,  such  as  the  ceiling  of 
old  buildings,  the  capping  has  a  tendency  to  spring  away  from  the  back- 
ing. This  may  be  overcome  by  the  use  of  two  or  three  straps  fastened 


198  HANDBOOK  OF  ELECTRICAL  METHODS 

over  each  length.  If  the  capping  of  the  molding  is  loose,  it  should  be 
removed  from  the  backing  and  tightened  by  tapping  it  with  a  mallet  or 
hammer  at  points  about  8  in.  apart  but  on  one  edge  only. 

Metal  molding  can  be  mitered  for  elbows  and  bends  by  cutting  it 
with  a  hack-saw.  Elbows  and  bends  thus  made  have  the  advantage  that 
they  fit  into  corners  more  closely  than  do  the  purchased  fittings.  Elec- 
trical conductivity  ie  preserved  by  always  leaving  a  portion  of  the  backing 
intact. 

Wiring  in  Cold-storage  Rooms  (By  W.  J.  Canada). — If  conduit  is 
employed  for  wiring  in  cold-storage  rooms,  the  effects  of  condensation 
should  be  minimized  by  the  following  general  precautions: 

1.  Place  all  circuit  fuses  and  switches  outside  of  the  rooms  in  substan- 
tial cabinets.     The  practice  of  using  in  the  rooms  cabinets  kept  partially 
dry  by  incandescent  lamps  is  a  poor  palliative. 

2.  Use  " brewery"  cord  and  weatherproof  keyless  sockets.     Attach 
the  cords  to  the  circuit  wires  mechanically  in  condulets  or  outlet  boxes, 
solder  them  carefully,  and  warm  the  rubber  tape  in  applying  it. 

3.  Incline  the  conduit  toward  the  outlet  and  junction  boxes  and 
leave  these  with  opening  to  drain  the  attached  conduit  lengths,  not, 
however,  allowing  them  to  drip  in  the  attached  sockets. 

4.  Repaint  the  conduit  carefully  at  all  joints  and  fittings,  avoid  short 
bends  and  repaint  the  entire  conduit  runs  occasionally. 

5.  Have   the   conduit  thoroughly   bonded  and  grounded  and  test 
occasionally  for  leakage  to  and  from  the  conduit. 

6.  Use  alternating  current  if  possible  rather  than  direct  current. 
Where  conditions  seem  to  indicate   the   desirability  of   using  open 

wiring,  the  following  precautions  will  enhance  the  minimization  of  leak- 
age for  which  this  construction  is  alone  employed  and  will  tend  to  the 
reduction  of  chance  grounds,  crosses  and  injuries  from  mechanical 
disturbances: 

1 .  Place  the  fuses  and  switches  in  substantial  cabinets  outside  of  the 
rooms. 

2.  Use  " brewery''  cord  and  weatherproof  keyless  sockets,  supporting 
them  directly  from  the  wires,  using  carefully  made  joints,  well  cleaned, 
soldered  and  with  the  rubber  tape  applied  warm  completely  covering  the 
joints. 

3.  Support  the  circuit  wires  on  petticoated  insulators,  maintaining 
unusual   separation   between   the   wires.     Attach   the   cords   near   the 
insulating  supports. 

4.  Where  it  is  necessary  to  use  bushings,  if  no  mechanical  injury  is 
anticipated  and  the  wire  leaves  the  bushing  parallel  with  it,  use  long 
porcelain  tubes  with  at  least  3  in.  projecting  on  either  side  of  the  material 
through  which  the  bushing  passes.     If  mechanical  injury  may  occur,  use 


INTERIOR  WIRING  199 

properly  drained  conduit  with  the  terminal  condulet  properly  separating 
the  wires  and  serving  as  a  drip  fitting.  Where  ice  or  frost  accumulates 
conduit  should  be  used  because  tubes  are  frequently  broken  in  such 
locations. 

5.  Where  much  dripping  from  the  ceiling  occurs  inverted  wood  or 
metal  trough  should  be  placed  over  the  wires. 

In  either  class  of  wiring  the  use  of  portable  cords  should  be  restricted, 
and  if  necessary  marine  cord  and  heavy  guarded  hand  lamps  should  be 
used.  It  is  frequently  found  that  carefully  made  joints  suffer  less  than 
expected  from  condensation  and  early  development  of  grounds,  and  for 
this  reason  conduit  is  gaining  favor. 

Direct-current  systems  are  not  desirable  for  breweries,  packing  plants, 
creameries,  etc.,  owing  to  the  liability  of  trouble  from  commutators  and 
brush  rigging.  Conduit  wiring  for  alternating-current  distribution  will 
be  the  type  favored  for  future  cold-storage  plants. 


FIG.  1. — LOOMED  WIRES  IN  CONDUIT. 

Conduit  Versus  Openwork  in  places  Subject  to  Moisture,  Corrosive 
Fumes,  Steam,  Etc.  (By  F.  G.  Waldenfels). — The  methods  described 
have  been  found  especially  serviceable  in  wet  places,  hide  cellars,  tank 
rooms,  fertilizer  plants,  glue  houses,  salt  storages,  casing  rooms,  exces- 
sively hot  or  cold  places,  etc. 

Where  ceilings  are  low  the  employees  extinguish  the  lights  by  turning 
the  lamp  in  the  socket,  thereby  twisting  the  joints  on  the  drop  wires 
until  the  bare  wires  come  together,  causing  a  short-circuit  and  possibly 
flames  that  will  feed  along  the  conductors  and  set  fire  to  combustible 
material.  If  the  joints  are  not  properly  made,  taped  and  then  com- 
pounded, any  amount  of  trouble  can  emanate  from  them.  For  such 
installations  it  is  recommended  that  composition  or  hard  rubber  sockets 
be  used.  Porcelain  sockets  are  too  fragile  in  low  places  and  are  better 
suited  for  high  ceilings.  Corrosion  can  be  greatly  reduced  in  cabinets 
if  the  latter  are  maintained  as  dry  as  possible  by  keeping  a  lamp  burning 
in  each  all  the  time.  Snap-switch  covers  could  be  painted  with  asphaltum 

14 


200  HANDBOOK  OF  ELECTRICAL  METHODS 

or  lacquer;  the  knife-switch  'blades  could  be  painted  with  vaseline 
or  lacquer;  in  fact,  all  the  terminals  on  the  cut-outs,  etc.,  could  be  coated 
with  vaseline  to  good  advantage.  Strange  to  say,  brass  T.  &  H.  base- 
key  sockets  when  protected  have  given  better  results  in  wet  and  steamy 
places  than  weatherproof  sockets.  They  were  first  painted  with  white 
lead,  then  taped  with  friction  tape,  then  painted  again  with  white  lead 
or  asphaltum.  The  No.  14  stranded  wires  entering  the  3/8-in.  cap  of 
the  socket  were  first  taped  and  then  treated  with  compound  to  keep  out 
the  moisture.  This  gave  a  non-corrosive,  unbreakable  socket  and  the 
lamp  circuit  could  be  opened  or  closed  with  a  key. 

Corrosive  Fumes  and  Salty  Atmosphere. — Open  wiring  has  always 
been  installed  in  packing  houses  and  other  places  subject  to  corrosive 
fumes,  but  there  are  several  plants  where  sherardized  and  galvanized 
conduit  have  been  in  use  for  more  than  two  years  with  very  good  results. 
In  places  full  of  salty  atmosphere,  open  work  reigns  supreme,  but  in 
spite  of  this  fact  some  conduit  is  installed  for  the  mains  and  rises,  and 
this  is  holding  out  as  well  as  the  open  work.  The  wires  come  from  the 
floor  above,  in  circular  loom,  which  is  inclosed  in  common  galvanized- 
iron  water  pipe.  (See  Fig.  1.)  The  loom  and  the  pipe  are  taped  and 
shut  with  compound  at  the  top  to  exclude  water. 

In  hide  cellars,  the  ceilings  are  about  7  ft.  or  8  ft.  high  and  open 
wiring  is  in  the  way  and  therefore  always  subject  to  mechanical  injury. 
When  a  workman  wants  to  extinguish  any  lights  he  simply  turns  the 
lamp  in  the  weatherproof  socket.  This  continual  twisting  finally 
affects  the  wires  at  the  joints,  breaking  the  strands  one  by  one  until  the 
current  is  carried  by  only  one  or  two  strands  of  each  polarity.  When  a 
circuit  is  reduced  to  this  condition  the  small  strands  heat  up  or  a  short- 
circuit  occurs  and  the  ensuing  fire  readily  runs  up  the  wires  to  the  ceiling. 
The  iron  screws  in  the  knobs  are  also  attacked  by  the  salty  water, 
causing  them  to  rust  and  expand,  thereby  cracking  the  knobs,  especially 
if  they  are  of  glass,  and  allowing  the  wires  to  drop.  In  casing  rooms  an 
acidulous  paste  coats  everything  and  destroys  the  insulation  of  wires 
and  motors. 

Pin  and  Insulator. — In  places  where  the  ceilings  are  high,  over  9  ft., 
the  pin  and  insulator  system  has  given  the  best  results,  as  far  as  insulating 
qualities  are  concerned;  but  this  method  of  wiring  requires  much  space 
and  is  constantly  disturbed  by  the  pipe  fitter  and  mechanic.  The 
construction  is  as  follows:  The  hangers  and  cross-pieces  are  of  2-in.  by 
4-in.  lumber,  dressed  and  painted  with  red  mineral  paint.  The  pieces 
are  fastened  together  with  3/8-in.  galvanized-iron  bolts,  and  the  insulator 
pins  are  set  and  fit  in  holes  in  the  cross-piece.  Ordinary  glass  petticoat 
insulators  are  screwed  on  the  pin  and  No.  12  B.  &  S.  gage  wire  with 
a  3/32-in.  rubber  insulation  is  employed.  It  will  be  observed  that  the 


INTERIOR  WIRING  201 

rubber  is  just  twice  the  thickness  of  ordinary  No.  12  wire.  Tie  wires 
are  employed  to  fasten  the  line  wire  to  the  insulator  and  for  this  purpose 
two  ways  are  employed,  as  will  be  shown  later.  No.  14  stranded  rubber- 
covered  wires  are  used  for  the  drops,  and  they  are  generally  anchored 
from  a  standard  No.  41/2  split  knob.  This  knob  has  two  grooves  for 
the  wires,  while  at  the  same  time  separating  them  an  inch  before  being 
twisted.  Very  often  the  drops  are  anchored  from  the  line  wires  after  a 
few  turns,  before  being  fastened  to  the  joints,  but  in  this  case  such  a 
method  of  anchoring  is  discouraged.  The  joints  are  a  very  important 
feature  and  should  be  made  as  described  under  another  heading.  Com- 
position mica,  porcelain  or  hard-rubber  sockets  should  be  used. 

The  pin  and  insulator  system  of  wiring  costs  slightly  more  than  a 
conduit  installation.  The  extra  cost  arises  from  the  use  of  the  special 
3/32-in.  rubber-covered  wire,  which  amounts  to  about  $50  per  1000  ft., 
or  about  four  times  the  price  of  ordinary  rubber-covered  wire. 

Split  Knobs. — Since  1911  the  No.  4  1/2  split  knob  has  completely 
replaced  the  solid  knob  in  the  Chicago  territory.  It  surpasses  the  solid 
knob  in  that  it  does  away  with  knobs  and  eliminates  a  great  deal  of  the 
twisting  of  wires  around  knobs,  thus  prolonging  the  life  of  the  insulation. 
Beside,  there  is  a  saving  in  labor  because  with  split  knobs  it  is  necessary 
only  to  fasten  the  two  ends  and  then  fill  in  the  intervening  space  with  a 
knob  every  41/2  ft.  With  the  solid  knob  it  is  necessary  to  give  the 
wire  a  turn  around  each  knob,  but  with  the  split  knob  the  wire  goes 
straight  through  the  knob.  Different  sets  of  grooves  are  provided  for 
sizes  of  wires  from  No.  14  to  No.  8. 

Should  a  line  support  become  broken  or  knocked  loose,  the  line  wire 
remains  taut,  another  advantage  possessed  by  the  split  knob  over  the 
solid  knob.  On  the  ends  of  the  line  some  electricians  prefer  to  use  two 
solid  knobs  and  wrap  the  wires  around  them  figure-eight  fashion,  ending 
with  a  few  turns  around  the  line  wire.  A  good  electrician,  however,  can 
do  as  well  with  split  knobs.  The  No.  14  stranded  wire  drops  are  also 
anchored  from  a  No.  4  1/2  split  knob,  doing  away  with  the  knobs  that 
were  formerly  used  in  a  solid  knob  installation.  Fig.  2  illustrates  .a 
satisfactory  installation  of  knob  work. 

Fig.  3  shows  another  method  of  employing  split  knobs  for  line  sup- 
ports and  at  the  same  time  anchoring  the  drop  from  the  line  wires.  This 
is  a  very  good  scheme,  as  it  enables  one  to  do  away  with  the  anchor  knob. 
The  drop  is  anchored  by  giving  the  drop  wire  a  few  turns  in  front  of  the 
knob  and  a  few  turns  in  back  of  the  knob  before  making  the  joint.  There 
is,  however,  one  objection  to  this  scheme  in  that  when  an  extension  is 
attached  to  the  socket  all  the  strain  comes  on  one  wire. 

Inverted  "Tee." — Several  packing  plants  employ  the  inverted  "tee" 
method  of  wiring,  which  is  second  to  the  pin  and  insulator  for  good 


202 


HANDBOOK  OF  ELECTRICAL  METHODS 


insulating  qualities.  In  this  method  use  is  generally  made  of  the  No. 
4  1/2  split  knobs  for  the  line  supports.  The  wood  used  is  dressed  2-in. 
by  4-in.  lumber  painted  with  asphaltum.  The  knobs,  Fig.  4,  are  turned 
upward  so  that  the  water  cannot  constantly  run  down  them.  Weather- 
proof sockets  are  anchored  from  split  knobs  on  the  line  supports  in  the 
usual  manner.  This  wiring  is  more  expensive  than  the  ordinary  open 
work. 

Knobs  on  Running  Boards. — In  places  not  subject  to  excessive  mois- 
ture split  knobs  or  separable  knobs  on  running  boards  make  a  good 
installation.  When  passing  under  beams  or  other  obstructions  circular 
loom  is  employed  between  the  supports.  If  switch  legs  are  necessary, 


FIG.  2. 


FIG.  3. 


FIG.  6. 


No-10  Packinghouse 
Cord 


FIG.  4.  FIG.  5. 

FIG.    2. METHOD  OF  USING  SPLIT  KNOBS  FOR  SUPPORTING  LINE  WIRES  AND  DROPS. 

FIG.    3. METHOD  OF  ANCHORING  DROPS  FROM  LINE  SUPPORTS. 

FIG.    4. INVERTED  "TEE"  METHOD  OF  SUPPORTING  WIRES  WITH  SPLIT  KNOBS. 

FIG.    5. — METHOD  USED  FOR  INSTALLING  SPLIT  KNOBS  ON  RUNNING  BOARDS. 
FIG.    6. INVERTED-TROUGH  WIRING,  USING  SPLIT  KNOBS. 

they  may  be  run  down  the  wall  or  column  in  conduit,  and  snap  switches 
should  be  mounted  in  a  condulet. 

The  running  boards  are  made  of  dressed  lumber,  1  in.  by  6  in.,  and 
painted  with  asphaltum  or  mineral  paint.  They  afford  protection  from 
mechanical  injury.  If  packing  house  cord  is  used  for  the  drops,  it  is 
anchored  with  a  pair  of  single  wire  cleats,  but  if  stranded  No.  14  wire  is 
used  it  is  preferable  to  employ  No.  41/2  split  knobs  as  the  anchoring 
medium.  This  kind  of  construction  costs  about  as  much  as  conduit, 
and,  that  being  the  case,  galvanized  conduit  would  give  far  better  results 
if  properly  installed. 

Trough  Wiring. — In  excessively  wet  places  and  hide  cellars  inverted 


INTERIOR  WIRING  203 

wooden  troughs  (Fig.  6)  have  been'  installed  with  good  results.  In  order 
to  obtain  a  good  job  a  carpenter  should  install  the  troughing,  especially 
where  obstructions  are  encountered,  and  an  expert  electrician  should  do 
the  wiring.  Special  pains  must  be  taken  to  get  a  tight  waterproof  joint. 
The  trough  affords  protection  trom  mechanical  injury  and  keeps 
water  from  dropping  on  the  wires.  Supporting  blocks  are  placed  every 
4  1/2  ft.  and  the  troughing  is  screwed  to  them.  All  the  lumber  should 
be  dressed  and  painted.  The  supporting  blocks  should  be  2  in.  thick  by 
9  in.  wide  and  the  boards  1  in.  thick  by  6  in.  wide.  In  some  cases  the 
trough  alone  costs  6  cents  a  linear  foot.  When  to  this  is  added  the  cost 
of  the  labor  of  carpenter  and  electrician  it  will  be  evident  that  the  method 
is  very  expensive  and  costs  much  more  than  a  good  conduit  installation. 
A  small  V-shaped  block  is  screwed  to  the  under  side  of  the  trough  to 


FIG.    7. METHOD  OF  SUPPORTING  LINE  WIRE  WITH  SEPARABLE  KNOBS. 

hold  the  anchor  knobs.  No.  4  1/2  knobs  have  given  the  best  satisfaction 
for  line  supports  and  drop  anchors.  The  disadvantages  of  this  system 
are  that  the  wood  rots  rapidly  and  the  initial  expense  is  great.  In  one 
case  of  which  the  writer  has  knowledge  the  open  wiring  in  the  trough  had 
to  be  replaced  about  every  six  months.  Finally  the  chief  electrician 
became  tired  of  the  constant  rewiring  necessary,  and  in  1911  he  replaced 
the  open  wiring  with  galvanized  conduit  and  cast-iron  condulets.  No 
trouble  has  appeared  yet,  and  it  looks  as  if  it  would  last  a  few  more  years, 
although  the  conduit  is  in  a  very  wet  place  and  over  offal  tanks.  Trough 
wiring  can  very  easily  be  replaced  with  better  results  by  properly  install- 
ing the  right  kind  of  conduit. 

Guard  Strips. — On  low  ceilings  where  wires  are  subject  to  mechanical 
injury  guard  strips  have  served  very  well  in  many  places.  These  strips 
are  1  1/2  by  1  1/2  in.  square  and  are  placed  about  1  1/2  in.  from  the  outside 
of  each  wire. 


204 


HANDBOOK  OF  ELECTRICAL  METHODS 


Separable  Knobs. — The  separable-knob  construction  (Fig.  7)  makes 
an  excellent  job.  The  line  wires  are  fastened  at  the  ends  to  a  pair  of 
solid  knobs  (figure-eight  fashion);  then  separable  knobs  are  inserted 
every  41/2  ft.  When  the  cap  of  this  knob  is  screwed  up  tight  it  takes 
up  slack  in  the  wire,  an  advantage  possessed  by  this  type  or  knob  over 
others;  but  the  knob,  on  the  other  hand,  is  more  fragile  than  a  split  knob. 


FIG.    8. METHOD  OF  SUPPORTING  LINE  WIRES  AND  DROPS  WITH  SEPARABLE 

KNOBS. 

All  sizes  of  wires  from  No.  14  to  No.  8  B  &  S.  gage  can  be  used  with  this 
knob,  and  the  drop  is  generally  anchored  from  a  No.  4  1/2  split  knob, 
as  previously  describe. 

Fig  8  illustrates  another  method  of  installing  separable  knobs,  where 
they  are  shown  used  as  supports  for  line  wires  and  at  the  same  time  for 
drops.  This  makes  a  serviceable  installation  of  very  low  cost. 


FIG.    9. SINGLE  SOLID  PORCELAIN  SUPPORT  FOR  BOTH  LINE  WIRES  AND 

DROP. 

Solid  Porcelain  Support. — A  support  that  has  been  used  almost  ex- 
clusively in  one  plant  for  open  work  in  wet  and  steamy  places,  is  made 
of  solid  porcelain  so  thick  that  the  breakage  is  negligible.  It  costs  about 
four  times  as  much  as  a  split  knob  and  a  general  installation  costs  nearly 
as  much  as  a  conduit  job.  The  support  is  easily  installed  with  a  3/8-in. 
by  5  1/2-in.lag  screw.  The  insulator  carries  the  two  line  wires  and  a  place 


INTERIOR  WIRING  205 

is  also  reserved  for  the  drop,  which  can  be  anchored  from  the  line  sup- 
ports or  from  the  individual  part  of  the  support  reserved  for  it.  As  far  as 
supporting  the  wires  is  concerned,  an  installation  of  this  kind  does  not 
differ  much  from  the  old  solid  knobs  which  require  a  twist  of  the  wire 
around  e('ach  knob.  But  the  small  screws  have  been  eliminated  and 


FIG.    10. — COMMON  SPLICE.  FIG.    11. — TAPPING  A  LINE  WIRE. 

replaced  with  one  large  one,  and  instead  of  two  or  three  knobs  they  are 
all  molded  into  one.  The  lag  screws  are  dipped  in  compound  before 
being  used,  and  are  thereby  protected  from  corrosion. 

Iron  Brackets  for  Glass  Insulators. — The  original  wiring  of  one  packing 
house  was  installed  with  iron  brackets  and  glass  insulators  screwed  to  a 
wooden  pin,  but  this  proved  very  unsatisfactory.  In  places  subject 


FIG.    12. TAP  FOR  LARGE  WIRES. 

to  moisture  and  corrosive  fumes  the  metal  arms  practically  vanished, 
allowing  the  lines  to  fall;  the  wooden  pins  swelled  and  cracked  the  glass 
insulators;  the  iron  screws  holding  the  brackets  to  the  woodwork  also 
corroded  until  the  heads  fell  off,  allowing  the  brackets  to  hang  in  any 
way.  As  fast  as  the  circuits  in  this  installation  break  down  they  are 
being  replaced  with  circuits  wired  on  supports,  or  solid  porcelain  No. 


FIG.    13. SINGLE-TIE  METHOD.  FIG.    14. — BACK-TIE  METHOD. 

41/2  split  knobs,  and  lately  a  great  deal  of  the  best  conduit  has  been 
installed  in  the  very  worst  places  with  good  results. 

Joints. — Joints  should  be  made  as  follows:  When  cutting  the  in- 
sulation the  knife  should  be  drawn  slantingly  toward  the  wire,  not 
straight,  or  otherwise  the  wire  will  be  nicked.  The  joint  should  at  first 


206  HANDBOOK  OF  ELECTRICAL  METHODS 

be  so  spliced  as  to  be  both  mechanically  and  electrically  secure.  Fig. 
10  shows  how  a  common  splice  should  be  made,  Fig.  11  the  way  to  make  a 
tap  to  a  line  wire,  and  Fig.  12  one  way  to  tap  for  heavy  wires.  These 
joints  are  standard  and  are  approved  by  all  underwriters.  All  the  wires 
for  the  joints  should  be  scraped  perfectly  clean  and  free  from  insulation. 
In  Fig.  10  the  two  ends  are  given  several  complete  long  turns,  then  the 
ends  are  given  four  complete  short  wraps.  In  Fig.  11  the  wire  is  given 
two  long  turns  for  play  room,  then  four  short  turns.  In  Fig.  12  the 
wires  are  bound  together  with  a  layer  of  No.  12  or  No.  10  bare  copper 
wire  closely  wrapped.  In  all  cases  the  joints  should  be  cleaned  with  a 
standard  soldering  flux  and  soldered  with  pure  half-and-half  solder. 

For  wet  and  steamy  places  the  bare  joint  after  being  soldered  should 
be  thoroughly  covered  with  insulating  compound,  which  acts  as  a  direct 
protection  from  moisture  should  water  leak  through  the  tape.  Then 
rubber  tape  should  cover  the  whole  joint,  followed  by  several  tight  layers 
of  friction  tape.  Then  for  a  good,  permanent  job  the  whole  joint  should 
be  waterproofed  by  completely  covering  it  with  an  application  of  com- 
pound of  insulating  paint. 

Tie  Wires. — There  are  certain  ways  to  fasten  tie  wires  properly  to 
hold  line  wires  to  insulators  or  knobs.  Fig.  13  shows  top  and  side  views 
of  an  insulator  to  which  the  line  is  attached  by  the  well-known  single  tie, 
made  by  bending  a  piece  of  wire  about  12  in.  long  around  the  insulator 
and  under  the  line  wire  with  three  or  four  turns  on  each  side,  the  ends 
being  cut  off  close.  Fig.  14  shows  a  back  tie.  A  piece  of  wire  about  18 
in.  long  is  bent  around  the  insulator  under  the  line  wire  with  4  in.  of 
tie  on  one  side  and  the  remainder  on  the  other.  The  short  end  is  then 
wrapped  three  times  around  the  long  wire,  leaving  a  space  equal  to  the  di- 
ameter of  the  wire  between  each  of  the  wraps.  The  long  end  is  wound 
closely  around  the  line  wire  two  times,  brought  back  around  the  insulator 
and  wrapped  three  times  around  the  line  wire  between  the  turns  of  the 
short  end. 

Wires. — The  kind  of  wire  used  for  open  work  is  a  very  important 
feature  of  the  installation.  The  rubber  insulation  must,  to  stand  the 
severe  conditions  of  moisture,  salty  atmosphere  and  corrosive  fumes,  be 
of  very  best  quality.  Ordinary  single-braided  wire  with  3/64-in.  rubber 
insulation  would  soon  break  down,  but  wire  with  3/32-in.  rubber  insula- 
tion having  in  it  about  30  per  cent,  para  and  being  triple  braided,  gives 
very  good  results  if  the  wiring  is  not  subjected  to  mechanical  injury. 
The  cost  of  this  special  wire,  however,  is  about  $50  per  1000  ft.,  several 
times  that  of  ordinary  No.  14  rubber-covered  wire,  but  the  results  obtained 
more  than  compensate  for  the  higher  cost.  With  this  heavy  insulation 
No.  12  wire  is  generally  used  for  branches.  If  conduit  were  installed, 
the  ordinary  rubber-covered,  double-braided  duplex  No.  14  New  Code 


INTERIOR  WIRING 


207 


wire  would  give  as  good  results,  and  the  wires  would  always  be  in  a  safe 
place. 

Wires  for  Drops. — Best  results  have  been  obtained  by  using  a  pair  of 
stranded  No.  14  rubber-covered,  single-braided  wires  for  drop  lamps. 
Ordinary  commercial  cord  will  not  answer,  and  No.  16  rubber-covered, 
single-braided  solid  fixture  wires  (twisted  pair)  have  been  used  most 
extensively  in  one  plant  in  connection  with  taped  and  painted  brass 
T.  &  H.  base-key  sockets,  with  satisfaction.  For  long  drops  packing- 
house cord  is  very  good  and  is  sometimes  used,  but  it  should  be  anchored 
with  a  pair  of  single  wire  cleats,  otherwise  it  is  difficult  to  provide  and 
a  good  support. 

Lead-covered  Wires. — Many  installations  employ  lead-covered  wires 
supported  on  knobs  and  others  where  the  lead-covered  wires  are  inclosed 
in  conduit.  Each  wire  has  a  rubber  insulation  over  which  is  a  lead  sheath. 
The  lead  affords  a  good  protection  from  salty  atmosphere,  acids  and  mois- 


FIGS.     15,    16,    17,    18  AND   19. WEATHERPROOF  AND  VAPORPROOF  SOCKETS. 

ture.  When  supported  on  knobs,  for  fear  of  grounds  collecting  on  the 
lead  sheath  which  would  make  it  alive,  short  strips  of  the  lead  are  care- 
fully cut  from  the  wire,  .the  spaces  being  taped  and  painted  or  compounded 
to  keep  the  moisture  from  entering  between  the  lead  and  the  rubber.  In 
some  fertilizer  rooms  open  work  with  lead-covered  wire  on  knobs  has  not 
given  the  satisfaction  expected.  The  wires  were  disturbed  and  broken 
by  mechanical  injury,  making  the  installation  very  hard  to  repair;  but 
on  the  other  hand  the  lead  affords  a  very  good  protection  to  the  insulation 
from  the  peculiar  acid  and  moisture  found  in  such  places.  Where  taps  to 
the  lead-covered  wires  are  made  for  the  drops  the  joints  should  be  care- 
fully compounded,  taped  with  rubber  and  friction  tape  and  then  com- 
pounded again.  It  is  essential  in  such  work  that  every  bit  of  the  surface 
of  the  finished  joints  be  covered  with  compound,  because  if  there  is  a 
slight  opening  water  and  acid  will  eat  through  the  tape  and  attack  the 
copper,  converting  it  into  copper  sulphate. 


208  HANDBOOK  OF  ELECTRICAL  METHODS 

Lead-covered  cables  have  also  been  employed  in  several  buildings  as 
risers.  In  some  cases  the  cable  is  inclosed  in  a  length  of  conduit  which 
extends  2  ft.  below  and  8  ft.  above  the  floors  on  the  side  wall  as  a  protection 
from  mechanical  injury,  the  cable  for  the  rest  of  the  distance  to  the  ceiling 
being  supported  on  knobs.  In  other  cases  the  cable  is  closed  in  continu- 
ous conduit  throughout  all  the  risers.  As  a  whole  an  open  lead-covered 
installation  is  very  undesirable. 

Sockets. — The  choice  of  sockets  is  more  or  less  a  gamble.  Porcelain 
weatherproof  sockets  are  fragile  and  cannot  stand  rough  usage.  Many 
porcelain  sockets  can  be  found  broken  after  six  months  because  moisture 
runs  down  the  wires  into  the  top  of  the  socket  and  with  the  assistance  of 
heat  finally  cracks  it.  On  many  old  porcelain  sockets  a  sulphur  compound 
was  used  for  sealing  purposes,  and  this  when  moistened  caused  the  socket 
to  crack  on  a  change  of  temperature.  The  newer  sockets  have  a  filling 
compound  which  will  not  crack  the  socket  when  subject  to  moisture  and 
heat. 


FIG.  20. CONDUIT  BOX  SOCKET  AND  OUTLET. 

For  high  ceilings  in  wet  places,  where  the  drop  lamps  are  out  of  reach, 
composition  and  mica  sockets  have  lasted  very  well.  No  sulphur  is 
used  in  these  sockets  for  sealing  purposes,  and  therefore  they  do  not 
crack  open  easily;  but,  on  the  other  hand,  excessive  heat  will  melt  them. 
On  low  ceilings,  however,  pigtail  sockets  should  not  be  used,  because 
of  the  twisting  of  the  joints  due  to  the  practice  of  switching  the  lamp  on 
and  off  by  turning  it  in  the  socket.  The  hard-rubber  molded  or  mica 
sockets,  however,  are  best  and  cheapest  for  use  on  reasonably  high 
ceilings  in  wet  places.  They  will  not  crack  like  porcelain  sockets,  can 
withstand  extra  hard  usage  and  are  constructed  even  better  than  the 
vaporproof  socket  by  having  a  solid  body  of  composition  supporting  the 
shell. 

Vaporproof  sockets  give  fair  results  if  the  outer  globe  is  always  on 
and  if  they  are  not  exposed  to  mechanical  injury.  They  cannot  with- 
stand any  hard  usage,  however,  and  this  is  a  requirement  which  generally 
must  be  fulfilled  in  steamy  places.  The  main  trouble  is  that  the  screw 
shell  is  not  properly  surrounded  with  a  porcelain  body,  and  the  bare 
shell  is  too  weak  for  ordinary  use. 


INTERIOR  WIRING 


209 


Rigid  weatherproof  sockets  when  installed  in  outlet  boxes  give  satis- 
faction, especialty  on  low  ceilings  where  the  employees  habitually  extin- 
guish the  lights  by  turning  the  lamps  in  the  sockets.  The  porcelain 
part  of  the  socket  should  be  notched  and  fitted  into  a  notched  metal 
cover  to  prevent  the  socket  from  turning.  Of  course,  where  the  ceilings 


FIG.    21. WEATHERPROOF  CEILING  CLUSTER. 

are  high  and  the  lamps  controlled  by  switches  are  out  of  reach  the  drops 
are  not  so  objectionable. 

On  very  low  ceilings,  where  a  rigidly  supported  lamp  and  receptacle 
are  impracticable  on  account  of  liability  to  mechanical  injury,  it  is  advis- 
able to  install  conduit  with  porcelain  covers,  which  permit  the  use  of  short 
pigtail  weatherproof  sockets,  without  joints  between  the  lamp  and  the 


-Joist 


FIG.  22. METHOD  OF  HANG- 
ING LAMP  CLUSTER. 


FTG.   23. — VAPOR-PROOF 
INCANDESCENT  LAMP. 


FIG.    24. 

ADAPTER. 


porcelain  cover.  Pressed-steel  condulets  give  excellent  results  because 
they  do  not  break  at  the  shoulder  if  there  should  happen  to  be  a  side 
strain  on  the  conduit,  although  they  frequently  crack  in  the  seams.  For 
protection  against  moisture  and  corrosive  fumes,  however,  the  cast-iron 
outlet  box  or  condulet  has  not  been  excelled.  There  is  also  a  sherardized 


210  HANDBOOK  OF  ELECTRICAL  METHODS 

steel  condulet  and  outlet  box  on  the  market  that  has  given  good  results 
in  such  places.  When  lamp  sockets  are  empty  it  is  wise  to  plug  them 
with  a  tight-fitting  cork  to  keep  them  from  corroding. 

Clusters. — Waterproof  clusters  are  employed  to  great  advantage 
where  the  ceilings  are  at  least  of  medium  height.  Clusters  that  have 
given  the  best  results  have  been  equipped  with  an  enameled  shade. 
They  are  made  up  with  a  1/2-in.  pipe  stem  about  12  in.  long  and  are  fitted 
with  a  porcelain  body  for  the  lamp  receptacles,  or  with  individual  sockets 
protected  by  a  white  enameled  shield,  which  permits  the  sockets  to  pro- 
ject through  it  about  1/4  in.  Extensions  can  be  attached  to  these 
clusters  without  harm.  The  clusters  are  generally  hung  from  a  hook 
in  a  swinging  position — a  very  favorable  feature.  Where  corrosive 
vapors  abound,  it  is  advisable  to  suspend  the  clusters  from  malleable- 
iron  or  cast-iron  hooks. 

Another  method  of  hanging  a  cluster  so  as  to  allow  it  to  swing  in 
two  directions  only  is  shown  in  Fig.  22.  Here  two  pieces  of  pipe  fas- 
tened to  a  T-condulet  are  strapped  to  two  floor  joists  and  the  pipe  stem 
of  the  cluster  is  screwed  into  the  condulet. 

Incandescent  Lamps  and  Adapters. — The  type  of  incandescent  lamp 
in  general  use  has  an  Edison,  or  screw,  base,  but  the  T-H,  or  bayonet, 
base  lamp  has  given  the  least  trouble.  As  a  protection  to  life  the  T-H- 
base  lamp  is  the  safest  to  use  in  wet  places,  because  there  is  no  live  screw 
shell  to  come  in  contact  with  as  in  the  case  of  an  Edison-base  lamp,  in 
which  the  shell  is  continued  from  the  socket  to  the  lamp  and  very  often 
projects  beyond  the  socket  about  1/4  in.  The  projecting  shell  is  fraught 
with  danger  to  employees,  especially  where  220-volt  alternating-current 
circuits  are  used  for  lighting.  Rather  than  pay  the  extra  3  cents  per 
lamp  several  packing  plants  have  switched  over  to  the  Edison  base  by 
using  adapters  or  have  replaced  the  T-H  socket  entirely  with  a  weather- 
proof Edison  base  socket . 

Edison-base  adapters  have  recently  been  employed  where  a  change 
has  been  made  from  the  T-H  base  lamp  with  poor  results.  There  are 
many  reasons  for  this:  first,  the  lining  of  the  adapter  absorbs  moisture 
like  a  sponge,  causing  short-circuits  in  the  sockets;  second,  if  a  lamp  is 
unscrewed  with  the  circuit  alive  the  arc  holds  and  burns  the  thin  contact 
ring  in  the  base  of  the  adapter;  third,  if  in  a  brass-taped  and  painted 
key  socket  equipped  with  an  adapter  the  circuit  to  the  lamp  is  interrupted 
by  means  of  the  key,  the  arc  will  invariably  hold  on  220  volts  and  burn 
off  the  metal  ring  in  the  base  of  the  adapter. 

Cut-outs  and  Snap  Switches. — On  110- volt  circuits  the  Edison-plug 
cut-outs  are  very  satisfactory,  provided  the  cut-out  bases  are  mounted  on 
1/2-in  porcelain  knobs,  cleats  or  hard-rubber  tubing.  Not  to  mount  them 
would  be  folly  and  cause  no  end  of  trouble  due  to  the  film  of  mois- 


INTERIOR  WIRING 


211 


ture  which  forms  between  the  terminals  and  the  material  of  the  wet 
cabinet  and  readily  affords  a  path  for  the  passage  of  electricity. 

Fuses. — Some  electricians  prefer  the  inclosed  cartridge-plug  fuse, 
claiming  that  its  use  limits  any  chance  of  employees  getting  a  shock  when 
the  fuses  are  backed  out  of  the  receptacle,  because  of  the  large  porcelain 
cap  which  fits  over  the  plug.  Until  recently  these  fuses  were  approved 
for  use  on  220-volt  circuits.  They  were  a  great  deal  safer  to  handle  in 


FIGS.    25,  26  AND  27. CARTRIDGE-PLUG  FUSE  AND  CUT-OUTS. 

wet  places  than  the  ordinary  cartridge  fuse  of  to-day,  but  one  great  dis- 
advantage is  that  an  inspector  cannot  tell  the  size  of  the  fuse  in  them. 

For  220-volt  lighting  circuits  in  damp  places  cartridge  fuses  and 
porcelain  bases  are  required  by  the  Chicago  underwriters.  The  bases 
should  also  be  mounted  on  1/2-in.  porcelain  knobs,  cleats  or  hard  rubber. 
Pains  must  be  taken  to  see  that  the  ferrule  contacts  fit  tightly  around 


FIGS.    28,  29  AND  30. FUSE  CUT-OUTS. 

the  fuse.  In  this  case  also  the  inspector  must  guess  at  the  size  of  the 
fuse  in  the  cartridge.  If  the  cut-out  cabinet  is  tight  and  well  constructed 
the  underwriters  would  under  most  circumstances  prefer  link  fuses  with 
copper  tips,  provided  there  was  a  barrier  between  each  set  to  keep  the 
hot  metal  from  the  fused  one  from  reaching  an  adjacent  fuse.  Par- 


212 


HANDBOOK  OF  ELECTRICAL  METHODS 


ticular  pains  should  be  taken  to  fasten  wires  under  all  terminals  properly, 
because  a  loose  contact  causes  heat  and  very  often  melts  the  fuse. 

Up  to  60  amp.,  250  to  600  volts,  the  ferrule-contact  cartridge  fuse 
may  be  used  for  motors,  provided  the  proper  spacings  are  kept  for  the 
different  currents  and  voltages,  and  from  60  amp.  to  600  amp.,  250  volts, 
and  to  400  amp..  600  volts,  the  knife-blade  contact  must  be  used,  provided 
the  proper  spacings  as  specified  in  the  National  Electrical  Code  are 
followed.  These  fuses  render  good  service  for  the  motors,  but  from  an 
inspection  standpoint  it  is  difficult  to  tell  what  size  of  fuse  wire  is  in  a 


FIGS.  31  AND  32. CARTRIDGE  FUSES  WITH  CUT-OUT  BASES. 

cut-out  that  has  been  refilled  without  removing  it  from  the  base,  thereby 
necessitating  the  stopping  of  the  machinery  to  examine  it.  Concealed 
fuses  create  a  doubtful  feeling  in  the  inspector,  and  many  inspectors 
would  prefer  good  link  fuses  to  refilled  cartridge  fuses,  provided  the 
cabinets  are  tight. 

On  heavy  circuits  it  is  imperative  to  note  that  all  the  strands  of  the 
cable  have  been  soldered  into  the  lugs  which  are  connected  to  fuse  bases, 
as  it  has  been  found  that  electricians  very  frequently  cut  off  the  outer 
strands  of  a  cable  to  make  the  latter  fit  a  certain  lug.  It  is  also  important 


FIG.    33. LINK  FUSES.. 


FIG.    34. SNAP  SWITCH. 


to  see  whether  cables  have  been  properly  sweated  into  lugs  during  the 
soldering  process  by  vigorously  shaking  the  cable  near  the  lug. 

Link  fuses  for  lamp  and  motor  circuits,  if  installed  in  good,  tight 
cabinets,  are  the  safest  and  most  satisfactory  protection  that  can  be 
employed  in  packing  houses.  It  is  also  very  easy  in  such  installations 
for  the  electrician  or  the  inspector  to  assure  himself  that  a  wire  is  not 
over-fused  and  that  the  motors  and  devices  on  those  circuits  are  therefore 
well  protected  from  overloads.  Slate  or  marble  bases  must  be  employed 
for  link  fuses,  and  it  is  advisable  to  have  a  barrier  across  the  base  between 


INTERIOR  WIRING 


213 


the  breaking  gap.  All  link  fuses  should  be  provided  with  copper  tips, 
otherwise  a  good  contact  is  not  made  under  the  screw  terminal.  With 
large  link  fuses  it  is  advisable  to  note  that  the  proper  breaking  distance 
has  been  maintained  across  the  gap,  otherwise  if  the  fuse  blows  the  metal 
will  crystallize  across  the  gap,  permitting  leakage  of  current. 

Snap  and  Knife  Switches. — For  lamp  circuits  snap  switches  are  safest 
and  fulfil  the  requirements.  Small  knife  switches  are  too  dangerous  in 
damp  places,  especially  where  foreign  laborers  are  employed.  The 
greatest  trouble  experienced  with  the  ordinary  snap  switches  is  due  to 
the  paper  lining  under  the  metal  shell.  This  absorbs  moisture,  swells 
and  causes  short-circuits  between  the  screw  terminals  inside  and  the  out- 
side metal  shell.  To  prevent  corrosion,  the  metal  cover  should  be 
treated  with  a  coat  of  asphaltum  or  lacquer.  All  snap  switches  should 
be  mounted  on  1/2-in.  porcelain  knobs,  cleats  or  hard-rubber  tubing. 


FIG.    35. FUSED  KNIFE  SWITCHES. 

Snap  switches  with  porcelain  shells  have  not  proved  satisfactory  in  pack- 
ing houses  on  account  of  rough  usage.  It  is  advantageous  to  have  the 
key  work  on  a  socket  so  made  that  it  cannot  be  unscrewed.  There  is, 
however,  a  snap  switch  for  wet  places  on  the  market  that  has  a  composi- 
tion hard-rubber  cap  1/8  in.  thick,  and  covers  to  fit  different  switches 
can  be  bought  separately. 

On  an  ordinary  knife  switch  several  defects  can  be  found  that  cause 
excessive  heating.  A  large  switch  that  is  frequently  opened  and  closed 
will  loosen  up  at  the  hinges;  the  nuts  also  work  loose,  releasing  the  spring 
washers,  and  very  often  the  lugs  or  wires  are  not  screwed  down  tight  at 
the  terminals.  All  these  defects  lead  to  heating. 

Electricians  frequently  use  a  heavy  pair  of  pliers  to  screw  a  small 
nut  down  on  a  wire.  If  too  much  force  is  used  the  threads  are  stripped 


214 


HANDBOOK  OF  ELECTRICAL  METHODS^ 


and  the  terminal  is  generally  left  in  that  state,  because  to  remedy  the 
defect  would  necessitate  taking  down  the  whole  switch  base  to  replace 
the  stripped  screw.  It  might  be  well  also  to  call  attention  to  the  car- 
tridge-fused knife  switch,  in  which  the  jaws  of  the  switch  are  at  the 
same  height  as  the  ferrule  or  knife-blade  contact  of  the  fuses.  When  the 
switch  is  opened  and  thrown  against  the  fuses  the  switch  handle  and 
blades  act  as  a  lever  and  wedge  against  the  fuses,  enlarging  the  clips  and 
causing  the  contacts  to  heat  when  in  circuit  because  of  the  loose 
connection. 

When  purchasing  switches  it  is  desirable  to  choose  those  of  heavy 
construction.  The  terminal  screws  should  be  heavy  enough  and  of  suffi- 
cient length  to  fasten  the  wire  or  lug  with  two  heavy  nuts,  one  of  which 
acts  as  a  lock  nut.  To  protect  switches  from  corroding  in  damp  places 
the  metal  parts  should  be  painted  with  lacquer  or  vaseline. 

Extensions,  Lamp  Guards,  Sockets,  Etc. — In  running  an  extension  in 
wet  places  packing-house  cord  or  elevator  cable  should  be  used.  It 
should  be  equipped  with  a  weatherproof  socket  inclosed  in  a  substantial 


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FIG.    36. STANDARD  WOOD  CUT-OUT  BOX. 

wooden  handle  having  a  strong  brass,  galvanized  or  bronze  guard,  with 
the  end  open  so  the  lamp  can  be  replaced  if  necessary.  At  the  other  end 
there  should  be  provided  an  approved  composition  or  hard-rubber, 
separable-cap  attachment  plug,  each  part  to  be  inclosed  in  a  brass  shell. 
Where  the  cord  enters  the  handle  and  cap  of  the  attachment  plug  it 
should  be  taped  and  compounded.  In  plants  operated  with  220  volts, 
alternating  current  for  lighting,  special  outlets  should  be  provided  for 
extensions  and  the  pressure  reduced  through  transformers  to  55  volts. 

Metal  guards  protect  the  lamps  from  breakage,  from  coming  in 
contact  with  combustible  material,  and  many  also  protect  the  lamp 
from  theft.  One  type  is  locked  to  the  socket  with  a  key.  For  protec- 
tion against  corrosion  the  metal  should  be  hot  galvanized  iron  or  brass. 
For  outside  use  where  exposed  to  the  elements,  copper-plated  lamp 
guards  have  given  the  best  results,  especially  around  cattle  pens. 

Wires  stay  up  only  about  as  long  as  the  screws  last.  Several  schemes 
of  treating  ordinary  steel  wood  screws  have  been  tried.  Hot  galvanizing 


INTERIOR  WIRING 


215 


has  given  good  results  except  that  threads  cannot  be  cleaned  very  well. 
Another  method  for  protecting  them  is  to  dip  the  screws  in  hot  compound 
or  insulating  paint.  Brass  screws  are  best  provided  the  heads  are  not 
broken  by  hammering  them  too  hard. 

In  packing  houses,  the  brushes  and  commutators  of  direct-current 
motors  cause  a  great  deal  of  trouble,  and  the  sliding  contacts  on  rheostats 
also  become  rough  and  burnt.  In  one  case  the  motors  had  to  be  re- 
placed so  often  that  finally  one  was  mounted  on  very  strong  brackets  on 
the  exterior  of  the  building  wall.  A  housing  of  hot  galvanized  metal 
large  enough  to  allow  a  man  to  pass  all  around  it  was  constructed  around 
the  motor  and  a  line  shaft  or  belt  run  through  the  wall  to  operate  the 
machinery  inside  the  building.  This  motor  (Nov.  1912)  has  now  been 
running  about  a  year  and  is  still  in  excellent  condition. 


lo     1  x  I  x  H  Ang.Iron  -^J1 


Brass  Hinges 


Brace 


Knob 


FIG.  37. ASBESTOS  WOOD  CABINET. 


In  fertilizer  buildings  direct-current  motors  seem  to  operate  well, 
except  when  they  heat  up  from  an  overload.  Then  it  seems  the  heat 
assists  the  fertilizer  powder  in  some  mysterious  way  to  break  down  the 
insulation  of  the  windings.  For  wet  places  the  alternating-current, 
squirrel-cage-type  motor  and  compensator  have  a  decided  advantage 
over  the  direct-current  equipment  because  of  the  absence  of  sliding 
contacts. 

Cabinets. — Wooden  cut-out  cabinets  in  the  past  have  had  the  prefer- 
ence in  most  packing  plants.  The  wood  is  mostly  7/8-in.  pine,  and  the 
inside  width  of  the  cabinet  is  generally  6  in.,  the  height  13  in.  and  15  in. 
when  a  pitched  roof  is  used,  and  the  length  varies  with  the  number  of 
cut-outs.  In  older  boxes  the  inside  is  lined  with  1/8-in.  or  1/4-in.  asbes- 
tos, fastened  with  3/4-in.  tacks  and  well  painted  with  asphaltum  or  in- 
sulating paint.  In  wet  places  the  top  is  made  slanting.  Other  boxes 

15 


216  HANDBOOK  OF  ELECTRICAL  METHODS 

are  constructed  with  the  bottom  2  or  3  in.  wider  than  the  top,  so  that 
the  door  will  always  have  a  tendency  to  swing  shut. 

Other  wooden  cabinets  have  the  top  and  bottom  of  the  same  width 
and  are  equipped  with  a  glass  door  which  is  raised  like  a  window.  The 
window  allows  the  switches  and  cut-outs  to  be  visible  all  the  time,  a  great 
convenience,  especially  when  a  lamp  is  kept  burning  inside  the  cabinet. 
This  light  acts  as  a  pilot  and  shows  the  way  to  the  cabinet  for  the  em- 
ployees, when  they  enter  the  place  in  the  dark  to  throw  on  the  circuits. 

All  cabinets  should  be  mounted  at  least  2  in.  from  the  wall  on  large 
flat  porcelain  knobs.  This  spacing  allows  plenty  of  ventilation,  a  great 
advantage  and  necessity  in  wet  places.  Small  and  medium-size  cabinets 
should  always  be  equipped  with  doors  so  mounted  that  gravity  will  tend 
to  close  them.  Catches  of  all  description  have  been  tried,  both  wooden 
and  metal,  to  keep  the  doors  closed,  but  none  as  yet  has  been  found  satis- 
factory. The  wooden  ones  are  broken  off  in  a  short  time  and  the  metal 
ones  corrode  off.  The  best  method  is  to  make  the  bottom  of  the  door 
heavier  than  the  top  by  fastening  a  metal  strip  along  the  outside  edge,  or 
provide  a  round  metal  weight,  allowing  it  to  act  at  the  same  time  for  a 
knob  with  which  to  raise  the  door.  All  kinds  of  hinges  have  been  tried, 
such  as  spring  hinges  and  leather  hinges  having  a  nail  through  a  metal 
strip,  steel,  galvanized,  etc.,  but  the  hot  galvanized  iron  or  brass  hinge  is 
best  in  packing-house  work. 

To  protect  employees  from  live  contacts,  some  companies  provide  an 
asbestos-lined  board  shield  in  front  of  the  knife  switches  and  fuses, 
mounted  on  two  wooden  pins  which  fit  in  holes  in  the  bottom  of  the  cabi- 
net. This  shield  may  be  lifted  out  of  its  place  when  access  to  the  fuses 
is  necessary. 

In  Fig.  37  it  will  be  observed  that  the  main  door  is  divided  into  two  parts. 
On  the  upper  door  there  is  a  barrier  projecting  at  right  angles  into  the  cabi- 
net. This  is  only  another  means  of  protecting  employees  from  coming  in 
contact  with  fuses  when  operating  snap  switches.  The  upper  compart- 
ment is  for  the  main  cut-out  and  all  the  fuses,  the  lower  one  is  for  snap 
switches  only.  The  upper  half  of  the  door  is  screwed  tight,  while  the 
lower  one  may  be  opened  any  time.  All  wooden  cabinets  are  now  lined 
with  1/8-in.  asbestos  board,  because  ordinary  asbestos  absorbs  too  much 
moisture,  no  matter  how  well  it  is  painted. 

Wires  should  enter  wooden  cabinets  preferably  at  the  bottom  through 
porcelain  tubes  properly  taped  and  compounded.  In  many  places  con- 
duit is  used  for  risers  and  branch  circuits,  in  connection  with  wooden 
cabinets.  The  conduit  for  the  branches  reaches  to  the  ceiling  only,  then 
the  circuit  is  continued  as  openwork.  In  cases  where  water  is  apt  to  run 
down  the  outside  of  the  pipe  into  the  cabinet  flooring  pitch  should  be 
poured  around  the  conduit  where  it  enters  the  cabinet. 


INTERIOR  WIRING  217 

Asbestos-wood  Cabinets. — It  is  essential  that  a  cut-out  cabinet  be  fire- 
proof, and  in  places  where  metal  cabinets  are  not  favored  a  cabinet  made 
entirely  of  asbestos  wood  could  be  employed  to  advantage.  Asbestos 
wood  is  unaffected  by  flames  or  intense  heat  of  any  form.  This  material 
will  not  warp  even  when  in  a  highly  heated  condition  water  is  thrown  on 
it,  and  in  addition  to  being  fireproof  it  is  also  moisture-proof.  It  is  ex- 
cellent for  cabinets,  and  in  one  large  plant  several  have  been  made  as  an 


FIG.    38. SWITCH  AND  FUSE  FIG.   39. HOT-GALVANIZED  STEEL 

CABINET.  CABINET. 

experiment  and  installed  in  a  tank  house.  The  construction  of  the  cabi- 
nets is  interesting.  At  first  an  angle-iron  frame  was  made  from  1-in.  by 
1-in.  by  1/8-in.  metal  and  fastened  with  copper  rivets.  The  thickness  of 
asbestos  wood  used  was  1/4  in.  and  3/8  in.,  the  3/8-in.  stuff  being  used 
for  the  top  and  doors.  Heavy  brass  hinges  were  employed  and  all  fast- 
enings were  made  with  copper  rivets.  The  asbestos  wood  running 
lengthwise  overlapped  the  sides.  Bushings  were  used  where  the  wires  en- 


/Service 

,  Cabinet  CO  F. 


(TO 


Condensation 

Cabinet 


FIG.    40. CONDENSATION  IN  CONDUIT  OVER  BOILERS. 

tered  the  bottom  of  the  cabinet.     The  cabinet,  which  was  constructed 
with  double  compartments,  cost  $6. 

Steel  and  Cast-iron  Cabinets. — Enameled-steel  cabinets  are  not 
satisfactory  for  damp  places,  being  susceptible  to  corrosion.  A  good  hot 
galvanized-steel  cabinet  of  No.  12  U.  S.  metal  gage,  however,  has  proved 
very  serviceable,  having  been  tried  in  one  of  the  worst  places — a  glue 
house.  In  this  place  a  steel  cabinet  was  installed  and  it  fell  to  pieces  in 


218  HANDBOOK  OF  ELECTRICAL  METHODS 

four  months.  Then  a  hot  galvanized  cabinet  replaced  it  over  a  year 
ago,  and  with  the  exception  of  turning  perfectly  white,  the  cabinet  looks 
as  good  as  the  day  it  was  installed.  The  steel  hinges,  however,  cor- 
roded away  and  had  to  be  replaced  with  brass  ones.  The  door  of  a  steel 
cabinet,  if  not  too  large,  should  close  by  gravity.  The  four  edges  of  the 
door  should  be  turned  at  right  angles  3/4  in.  and  close  against  a  rabbet  all 
around  the  box.  A  metal  stop  should  be  fastened  on  top  of  the  cabinet, 
so  that  the  door  cannot  be  raised  too  high  and  left  in  an  open  position. 
A  metal  strip  should  also  be  fastened  on  the  bottom  part  of  the  door 
to  act  as  a  weight.  One  can  rest  assured  that  this  kind  of  door  will  al- 
ways be  found  in  a  closed  position,  because  it  cannot  be  left  open  unless 
held  up  by  a  stick.  Such  a  cabinet  will  be  found  moisture-proof  and 
dust-tight. 

The  cast-iron  cabinet  is  on  a  par  with  the  hot  galvanized  steel  cabinet> 
as  far  as  service  is  concerned.  It  will  not  corrode,  but  it  costs  more  and 
will  break  easily.  With  conduit  installations  the  cast  iron  has  to  be 
drilled  for  each  pipe  where  with  the  steel  cabinet  the  knock-outs  are 
depended  upon  to  insert  the  conduit. 

Conduit. — Up  to  the  present  time  ordinary  conduit  has  been  charged 
with  two  deficiencies,  corrosion  and  condensation.  Whenever  ordinary 
conduit  was  installed  in  places  subject  to  moisture  and  corrosive  fumes  it 
invariably  corroded  and  scaled  off  very  readily,  leaving  only  the  shell  of 
the  conduit  hanging  on  the  wire.  In  this  state  the  insulation  of  the  wire 
also  soon  broke  down,  making  the  installation  hazardous. 

Experiments  with  all  kinds  of  conduit  have  been  carried  on  for  three 
years  in  a  place  where  conditions  are  severest.  With  the  different  kinds 
of  conduit  a  piece  of  hot  galvanized  water-pipe  was  also  installed,  after 
being  closely  examined  for  burrs  inside  the  pipe.  Strange  to  say,  all  the 
conduit  was  attacked  and  a  great  deal  of  it  was  completely  eaten  away,  but 
the  hot  galvanized  water-pipe  turned  white  and  is  still  doing  service  for  a 
motor,  having  three  alternating-current  feeders  in  it,  and  it  looks  as  good 
to-day  as  when  it  was  installed.  About  50  ft.  of  lead-covered  flexible 
steel-armored  conductor  was  tried  in  the  same  place,  with  water-tight 
fittings,  and  an  examination  after  four  months  showed  it  was  corroded, 
even  the  lead  straps  holding  the  cable  in  places  being  pitted. 

The  success  of  hot  galvanized  water-pipe  caused  the  writer  to  visit 
some  of  the  conduit  manufacturers,  with  a  view  to  encouraging  them  to 
manufacture  a  hot  galvanized  conduit.  One  company,  however,  had 
been  experimenting  for  the  last  four  years  trying  to  put  a  hot  galvanized 
conduit  on  the  market  at  the  same  price  as  the  other  conduit.  In  this 
it  was  evidently  successful  and  produced  a  hot  galvanized  pipe  that  could 
withstand  seven  to  ten  one-minute  dips  in  a  standard  solution  of  copper 
sulphate  at  a  temperature  of  65  deg.  Fahr.  Other  types  of  conduit  do 


INTERIOR  WIRING 


219 


well  if  they  can  withstand  five  one-minute  dips.  March,  1912,  a  sample 
of  the  hot  galvanized  conduit  was  nailed  to  a  joint  in  the  glue  house 
mentioned,  and  within  a  few  months  turned  white,  which  is  a  sign  of  long 
life,  no  corrosion  being  visible. 

Corrosion. — Ordinary  conduit  has  given  fairly  good  results  in  many 
places  where  the  worst  conditions  of  moisture,  etc.,  prevail;  but  some 
locations  are  more  severe  on  conduit  than  others.  In  several  places 
where  the  conditions  were  very  severe,  the  conduit  being  subjected  to 
steam,  ammonia  and  sulphur  fumes,  about  every  fifth  piece  of  conduit 
was  slightly  corroded  and  about  every  tenth  piece  of  length  was  corroded 
completely  through.  The  rest  of  the  conduit  turned  completely  white 
and  showed  no  signs  whatever  of  corrosion.  This  shows  that  all  conduit 
is  not  uniformly  treated  during  the  process  of  manufacture,  because  then 
none  of  it  would  have  corroded.  To  ward  off  corrosion  and  make  the 
ordinary  conduit  last  longer,  several  electricians  have  painted  the  conduit 


FIG.    41. INTERCEPTING  AIR  PASSAGES  IN  CONDUIT. 

before  installing  it.  Best  results  have  been  obtained  by  using  a  silicate 
graphite  paint.  Others  tried  insulating  paint  or  asphaltum  and  also 
obtained  good  results,  especially  where  the  conduit  was  exposed  to  the 
steam  from  the  hog.  Still  others  have  painted  the  conduit  with  aluminum 
paint  and  find  it  very  satisfactory  in  a  place  where  ordinary  conduit 
lasted  only  two  months. 

Despite  the  inequalities  of  ordinary  conduit  it  has  served  fairly  well. 
Of  course,  one  must  not  expect  too  much  from  an  ordinary  soft-steel  pipe, 
especially  in  places  where  conditions  are  very  severe.  Hot  galvanized 
pipe,  however,  has  persisted  in  places  where  the  ordinary  conduit  cannot 
stand  up  and  is  therefore  to  be  commended  for  packing-house  work. 

Condensation. — Condensation  can  be  eliminated  in  a  conduit  installa- 
tion in  two  ways — one  by  draining  the  conduit  between  outlets  by  gravity 
and  the  other  by  plugging  up  or  by  interrupting  the  air  passages  in  the 
conduit  at  positions  where  different  temperatures  are  encountered. 


220 


HANDBOOK  OF  ELECTRICAL  METHODS 


Where  steam  and  alternating  temperatures  prevail  condensation  is 
sure  to  exist,  and  in  such  a  case  the  conduit  should  be  drained  between 
the  outlets  by  installing  another  outlet  with  one  or  two  holes  in  the  por- 


no.   42. — PROVISION  FOR  DRAINING  CONDUIT. 

celain  cover  to  let  the  water  out.  Referring  to  Fig.  42,  it  will  be  observed 
that  there  is  a  drain  outlet  between  the  two  lamp  outlets,  and  also  that 
the  conduit  has  a  drop  toward  the  drain  outlet  so  the  water  can  run  out 


FIG.    43. — METHOD  OF  AVOIDING  CONDENSATION. 

by  gravity.     If  switch  legs  are  installed  on  the  walls  or  columns,  a  hole 
should  be  left  open  in  the  bottom  of  the  box. 

Fig.  44  shows  the  same  method  of  draining,  when  the  conduit  extends 
from  a  room  with  a  temperature  of  75  deg.  Fahr.  to  a  room  having  a 


INTERIOR  WIRING 


221 


temperature  of  34  deg.  Fahr.  Fig.  41  shows  another  method  whereby 
condensation  can  be  eliminated.  If  the  conduit  is  plugged  in  the  outlet 
at  the  partitions,  as  shown,  then  there  will  be  no  condensation.  Other- 
wise, if  the  air  passage  were  not  interrupted,  the  hot  and  cold  air  would 
come  together  and  condensation  take  place.  At  the  partition  an  outlet 
box  is  installed  in  the  conduit  system  and  the  pipe  is  plugged  up  and  care- 
fully sealed  with  insulating  compound.  This  work  should  be  very  care- 
fully done,  otherwise  if  there  is  only  a  small  air  passage  condensation  will 
take  place.  Fig.  43  shows  conduit  risers  for  branch  circuits  from  a  pas- 
sageway with  a  temperature  of  75  deg.  Fahr.  to  coolers  of  34  deg.  Fahr. 
Another  method  of  interrupting  the  system  is  to  end  with  outlet  boxes 
at  the  partition  and  piece  the  partitions  with  open  wiring  through  porce- 
lain tubes.  This  method  is  not,  however,  to  be  encouraged,  because  equal 


75  F. 


34  F. 
FIG.    44. METHOD  OF  DRAINING  CONDUIT. 

results  are  obtained  with  the  former  methods,  and  of  the  three  draining 
is  preferable. 

Cast-iron  Outlet  Boxes. — Cast-iron  outlet  boxes  should  be  installed  in 
wet  places,  because  a  steel  box  corrodes  too  readily.  The  conduit 
should  be  white-leaded  before  being  screwed  to  the  outlet  boxes  or 
jointed.  It  is  also  well  to  provide  a  gasket  between  the  cover  and  the 
boxes,  to  keep  the  water  from  the  joints  as  much  as  possible. 

Lead-covered  Flexible  Steel-armored  Cable. — Of  the  two  places  where 
50  ft.  of  lead-covered  flexible  armored  cable  was  installed,  one  was  in  a 
large  pickling  establishment,  where  salt  water  condenses  on  the  ceilings 
and  walls.  The  cable  after  thirty  months'  use  showed  not  the  slightest 
sign  of  corrosion.  The  other  50  ft.  of  cable  was  installed  in  a  glue  house, 
and  after  three  months'  use  was  corroded,  especially  that  portion  of  it 
over  the  liquid  tanks.  In  a  glue  room  everything  is  covered  with  an 
acidulous  paste,  which  readily  attacks  iron  and  steel,  but  galvanized 


222  HANDBOOK  OF  ELECTRICAL  METHODS 

metal  withstands  the  sulphur  and  ammonia  well.  Lead-covered,  steel- 
armored  cable,  however,  has  been  very  serviceable  in  a  great  many  other 
places. 

Conduit  Versus  Open  Wiring. — As  compared  with  regular  open  wiring, 
such  as  two-piece  knobs  and  ordinary  code  wire,  conduit  is  ordinarily 
about  twice  as  expensive.  As  compared  with  the  higher  class  of  open 
wiring,  such  as  the  inverted  "tee"  or  the  pin  and  insulator  system  using 
3-32-in.  rubber-covered  wire,  a  conduit  installation  is  cheaper,  the  pin 
and  insulator  system  costing  almost  twice  as  much.  Comparing  conduit 
work  with  a  job  using  split  knobs  on  running  boards,  the  cost  would  be 
about  the  same.  Considering  all  the  good  points  of  the  best  open  wiring 
and  not  mentioning  the  hazardous  ones,  from  an  underwriter's  viewpoint 
a  hot  galvanized  conduit  installation,  properly  installed,  is  at  least  100 
per  cent,  better. 

Instances  of  Condensation  in  Conduit. — To  show  the  effect  of  condensa- 
tion in  conduit,  a  few  packing-house  examples  are  cited  herewith.  In 
these  cases  the  water  was  trapped  in  the  conduit  at  its  lowest  point  and 
in  time  the  insulation  on  the  conductors  rotted  and  broke  down,  resulting 
in  a  short-circuit  or  a  ground  which  burned  a  hole  in  the  conduit.  The 
worst  cases  have  happened  at  service  entrances.  At  these  points  the 
conductors  enter  the  building  in  conduit,  there  being  no  fuse  between 
the  transformer  and  the  fused  service  switch.  If  a  short-circuit  or  a 
ground  occurred  between  these  two  devices,  it  would  have  to  burn  itself 
clear  either  by  melting  the  wires  or  by  puncturing  the  conduit.  On  the 
other  hand,  if  water  collects  in  a  conduit  where  the  circuits  are  equipped 
with  fuses,  the  fuses  provide  the  protection  desired,  in  case  the  regular 
fuse  has  not  been  replaced  with  a  strip  of  metal  or  copper  wire. 

In  one  case  of  condensation  which  happened  in  a  basement  ceiling 
over  some  boilers,  the  service  wires  in  conduit  entered  the  building  at 
the  ceiling  of  the  first  floor  and  passed  to  a  fairly  tight  cabinet  in  a  cold 
room  on  the  wall  about  5  ft.  above  the  first  floor,  where  was  installed  the 
fused  service  switch.  The  conduit  ran  from  the  cabinet  through  the  base- 
ment ceiling  and  along  the  ceiling  over  some  boilers  to  a  distributing 
cabinet.  When  cold  weather  came  the  fuses  in  the  service  cabinet  blew 
continually.  Investigation  showed  that  some  of  the  conduit  over  the 
boilers  was  full  of  water.  This  was  due  entirely  to  condensation.  Cold 
air  entered  at  the  service  pipe  and  traveled  down  through  the  service 
cabinet,  then  continued  until  it  encountered  the  hot  air  in  the  conduit 
above  the  boilers.  The  temperature  in  the  basement  was  very  high  and 
on  the  first  floor  it  was  very  low,  and  the  consequence  was  that  condensa- 
tion took  place  when  the  hot  and  cold  air  met.  The  trouble  was  elimi- 
nated by  providing  an  outlet  box  with  a  1/2-in.  hole  in  the  cover,  directly 
where  the  conduit  entered  the  ceiling  of  the  basement.  (See  Fig.  40.) 


INTERIOlfWIRING  223 

In  another  case  the  service  wires  entered  a  room  that  was  very  hot 
and  steamy.  The  circuits  for  the  lamps  in  this  room  were  wired  in  con- 
duit which  came  from  the  cut-outs  in  the  main  or  service  cabinet.  The 
result  was  that  the  cold  air  entered  the  service  conduit  from  the  outside 
and  traveled  along  until  it  entered  the  cabinet,  and  here  it  diffused  itself 
into  all  the  warm  conduits  in  the  room,  the  condensation  gathering  at 
the  lowest  part  of  th'e  pipe  system.  The  trouble  was  remedied  by  pro- 
viding an  outlet  box  at  the  point  where  the  conduit  entered  the  inside  of 
the  room  and  plugging  the  entering  pipe  with  compound.  (See  Fig.  41.) 

If  conduit  is  bent  around  the  beams  of  a  room  that  is  steamy  and  is 
subjected  to  alternating  temperatures,  condensation  is  sure  to  take  place, 
and  the  water  will  be  trapped  at  the  bends.  The  best  remedy  is  to  pro- 
vide a  "tee"  condulet  or  outlet  box  at  the  bend,  to  act  as  a  drain. 

To  drain  conduit  some  electricians  may  attempt  to  drill  holes  in  the 
pipe  at  the  lowest  point  in  the  line.  This  should  not  be  allowed,  because 
a  hole  drilled  through  the  shell  of  the  conduit  will  expose  the  plain  steel, 
which  is  not  galvanized,  and  in  a  very  short  time  the  hole  will  be  corroded 
shut,  thereby  ending  its  usefulness,  and  at  the  same  tine  damaging  the 
conduit. 

Installation  of  Conduit. — The  following  are  names  of  places  where 
conduit  has  been  installed,  with  remarks  as  to  the  life  and  condition  of 
the  conduit: 

Cold-storage  Warehouse. — Enameled  conduit  was  installed  seven  years 
ago  as  an  experiment.  Some  of  the  conduit  was  run  continuously  from 
the  cabinet  in  the  passageway  where  the  temperature  was  about  68  deg. 
Fahr.  to  the  cold-storage  rooms  having  a  temperature  10  deg.  below 
zero.  Some  of  the  conduit  was  plugged  shut  at  the  partition  in  the  pass- 
ageway. All  the  conduit  is  in  good  condition;  in  fact  it  all  looks  like  new, 
and  there  is  no  condensation  or  corrosion  in  either  case.  This  is  prob- 
ably due  to  the  extreme  cold  condition. 

Cooler  or  Hanging  Rooms. — This  is  a  room  where  the  cattle  hang  and 
steam  after  being  killed.  Sherardized  conduit  is  plugged  at  the  partitions 
as  shown  in  Fig.  41.  In  three  years  no  condensation  or  corrosion  is 
visible. 

Tank  Rooms. — In  these  places  the  offal  of  the  plant  is  boiled  over  into 
fertilizer  by  a  process  in  which  sulphur  and  ammonia  are  used.  The  steam 
readily  attacks  metals.  The  particular  building  in  question  is  constructed 
of  reinforced  concrete.  Exposed  sherardized  and  galvanized  conduit  was 
used  for  wiring  and  was  installed  two  and  one-half  years  ago.  Ninety 
per  cent,  of  both  types  approximately  turned  white  and  are  doing  good 
service;  the  other  10  per  cent,  of  both  types  of  conduit  was  practically 
eaten  away.  This  installation  was  made  in  the  usual  way  and  was  not 
drained  or  plugged.  About  90  per  cent,  is  holding  out  pretty  well  and 


224 


HANDBOOK  OF  ELECTRIC  METHODS 


that  a  long  life  is  assured  after  the  metal  turns  white.  The  other  10  per 
cent,  was  very  easily  replaced  with  little  cost. 

Glue  House.— Thus  far  no  kind  of  conduit,  except  some  hot  galvanized 
water  pipe,  used  as  an  experiment,  has  been  able  to  withstand  the  attacks 
of  fumes  in  this  place.  Every  kind  of  conduit  on  the  market  was  tried 
but  all  corroded  rapidly.  A  section  of  hot  galvanized  water  pipe  has  been 
in  service  three  years,  and  since  it  has  turned  white  it  will  probably  last 
many  more  years.  This  experiment  has  demonstrated  that  hot  galvan- 
ized pipe  is  what  must  be  installed  to  withstand  successfully  the  severest 
conditions  encountered  in  packing-house  work. 

Borax  Mill. — About  three  years  ago  a  room  in  which  borax  liquid  is 
allowed  to  steam  and  crystallize  was  wired  in  enameled  conduit.  The 
installation  is  still  in  excellent  condition  and  no  corrosion  whatever  is 
visible. 

Canning  Department. — A  canning  department  was  wired  with  enam- 
eled conduit  and  cast-iron  boxes  seven  years  ago.  Recent  inspection 
revealed  that  the  conduit  was  only  slightly  attacked  over  the  boiling 
tanks.  The  rest  was  in  excellent  condition. 


I  For  Combination  Fixtures 


Hickey 


II  For  Electroliers 


FIG     1. INSULATING  JOINTS. 


Pickling  Department. — In  this  place  salt  water  is  continually  condensed 
on  the  ceilings  and  walls.  Enameled  conduit  and  galvanized  conduit 
have  been  installed  fifteen  months  and  drained  as  shown  in  Fig.  42. 
Both  are  in  excellent  condition,  and  no  grounds  have  occurred  yet.  In 
another  instance  lead-sheathed,  flexible-steel  armored  conductors  had 
been  in  use  over  thirty  months  and  were  still  in  very  good  condition. 

Fertilizer  Rooms. — Several  are  wired  in  conduit  but  not  in  damp  or 
wet  places.  Any  first-grade  conduit  should  give  good  satisfaction.  Wet 
fertilizer  attacks  all  conduits  very  readily. 

Hair  House. — Conduit  has  given  good  results  with  cast-iron  boxes, 
except  in  dyeing  rooms  or  in  damp  places.  With  hot  galvanized  conduit, 
properly  drained,  it  should  be  feasible  to  wire  every  part  of  a  hair  house 
in  conduit. 

Oleo  and  Oil  Houses. — Conduit  gives  excellent  results  wherever  there 
is  plenty  of  grease.  Over  the  scrap  kettles  steam  had  caused  some 
trouble,  but  if  the  proper  conduit  is  employed  and  drained  no  trouble 
should  ensue. 


INTERIOR  WIRING 


225 


Insulating  and  Supporting  Fixtures  (By  R.  H.  Cronin). — Insulating 
joints  are  used  to  insulate  fixtures  from  grounded  parts  of  a  building. 
The  wiring  spaces  within  fixtures  are  so  confined  that  grounds  are  very 
liable  to  occur  in  them.  If  the  fixture  is  insulated  from  the  grounded 
parts,  one  ground  within  it  is  not  liable  to  do  harm.  Fig.  1  shows  some 


Conductors 
FIG.    2. INSULATING  JOINT  FOR  A  COMBINATION  FIXTURE. 


FIG.   3. — ELECTRIC  FIXTURE 
SUPPORT. 


Fixture 
"Stem 


FIG.    4. SUPPORT  FOR 

A  HEAVY  FIXTURE. 


insulating  joints.  That  at  I  is  used  for  combination  gas  and  electric 
fixtures.  It  has  a  hole  through  it  to  permit  the  passage  of  gas.  That 
shown  at  II  is  for  electroliers  and  has  no  hole  through  it. 

In  insulating  combination  fixtures  the  insulating  joint  should  be  lo- 
cated as  near  as  feasible  to  the  ceiling,  and  the  wire  ends  left  after  con- 


226  HANDBOOK  OF  ELECTRICAL  METHODS 

nee  ting  should  never  be  twisted  around  the  supporting  pipe  above  the 
joint.  (See  Fig.  2.)  Flexible  tubing  is  required  on  the  wires  in  knob 
and  tube  work  and  it  should  extend  below  the  joint.  The  code  requires  that 
the  pipe  above  the  joint  be  protected  with  insulating  tubing,  which  may 
be  either  a  heavy  wrapping  of  tape  or  circular  loom. 

Fixtures  can  be  supported  in  frame  buildings  by  the  method  of  Fig.  3. 
A  wooden  strip  or  cleat  should  be  fastened  just  above  the  lath  during  the 
construction  of  the  building  to  take  the  screws  to  hold  a  canopy  block. 
The  wooden  canopy  block  supports,  with  wooden  screws,  the  fixture  crow- 
foot and  insulates  the  canopy  from  the  ceiling.  A  screw  hook  turning 
into  a  joist  (Fig.  4)  can  be  used  for  sustaining  heavy  fixtures  in  frame 
buildings.  A  special  insulating  joint  having  an  eye  is  inserted  in  the  fix- 
ture stem  to  insulate  the  fixture  from  the  ceiling,  or  a  chandelier  loop  can 
be  used  on  a  regular  insulating  joint.  In  fireproof  buildings  where  fix- 


Iron  Strip      ^T  Nipple 


FIG.    5. SUPPORT  FROM  A  FIREPROOF  CEILING. 

tures  must  be  erected  after  the  building  is  completed  an  iron  strap  (Fig. 
5)  held  to  the  surface  of  the  ceiling  with  a  couple  of  toggle  bolts  can  be 
utilized  for  supporting  a  fixture.  A  pipe  or  conduit  nipple  turning 
into  a  threaded  hole  in  the  strap  takes  the  weight  of  the  fixture. 

Fixture  canopies  can  be  insulated  from  ceilings  and  walls  with  com- 
mercial canopy  insulators,  of  which  there  are  many  forms  on  the  market. 
Canopies  are  usually  supplied  already  fitted  with  insulating  rings  by  the 
fixture  manufacturers.  Where  canopy  insulators  must  be  " homemade" 
the  method  of  Fig.  6  or  that  of  Fig.  7  may  be  followed.  In  Fig.  6  a  ring 
of  fiber  formed  from  the  sheet  material  is  bent  to  fit  the  interior  of  the 
canopy  and  is  held  therein  with  wires  or  small  rivets.  The  ring  should 
extend  about  3/8  in.  above  the  top  edge  of  the  canopy.  Another  canopy 
insulator,  sometimes  termed  a  "bug"  insulator,  can  be  sawed  from  block 
fiber,  as  shown  in  Fig.  7.  The  upper  edge  of  the  canopy  rests  in  a  slot 


INTERIOR  WIRING 


227 


sawed  in  the  "bug."  At  least  three  such  insulators  should  be  used  for 
every  canopy.  A  small  nail  or  wire  driven  through  a  hole  in  the  insulator 
and  one  in  the  canopy  holds  each  "bug"  in  position. 

Connecting  Cords  in  Sockets  (By  C.  Broadhurst). — In  fastening 
cords  in  sockets  some  precaution  should  be  taken  to  prevent  stray  strands 
of  wire  from  coming  in  contact  with  metal  and  thereby  causing  short- 
circuits  or  grounds.  This  can  be  accomplished  by  dipping  the  bared 


Fiber  Ring 


Canopy 


Details 


Canopy 


FIG.    6. FIBER-RING  INSULATOR. 


Bug  Insulate 


Application 
FIG.    7. BUG  INSULATOR. 


conductor  of  the  cord  in  molten  solder  before  it  is  made  up  under  the  bind- 
ing screw.  Strips  of  tape  about  1/4  in.  wide,  torn  from  wider  pieces,  are 
sometimes  wound  about  the  braid  at  the  end  of  bared  cord,  to  prevent 
the  braid  from  unraveling.  A  fairly  good  method  of  fastening  a  cord  in 
a  socket  is  to  cut  half  of  the  conductor  away,  twist  the  remaining  strands 
into  a  little  cable  and  then  make  it  up  about  the  screw.  Tape  should  be 
applied  as  shown  in  the  illustrations,  Fig.  1. 


Lamp  Cord 


Tape 


Soldered 
Conductors 


Socket  Screw 


Taped  Cord  End 


Cut  these  off 

A 


\''-''- 


C 

Screw  Twisted  In 

FIG.    1. — FASTENING  CORDS  IN  SOCKETS. 

Electric  Vacuum  Cleaner  for  Fishing  Conduit. — A  Richmond  (Ind.) 
contractor  was  perplexed  as  to  how  to  "fish"  wires  through  a  0.375-in. 
gas  pipe  for  a  newel-post  lamp.  The  pipe  had  three  bends  in  it  and  could 
not  be  disconnected.  A  friend  suggested  to  him  that  he  get  an  electric 
vacuum  cleaner  on  the  job.  When  the  cleaner  was  brought  the  two  men 
took  a  piece  of  string  and  made  a  ball  of  the  string  nearly  as  large  as  the 
opening  in  the  pipe.  Leaving  the  remainder  of  the  string  attached,  they 
inserted  the  ball  in  one  end  of  the  pipe  and  put  the  smallest  nozzle  on 


228  HANDBOOK  OF  ELECTRICAL  METHODS 

the  cleaner  hose  at  the  other  end  and  sucked  it  through.  The  entire 
operation  took  about  two  minutes,  and  after  they  had  a  string  through  the 
pipe  they  were  able  to  draw  the  wires  after  it  without  any  further  trouble. 
By  this  method  they  accomplished  a  task  in  less  than  five  minutes  which 
a  man  had  tried  to  do  by  hand  for  the  greater  part  of  the  previous  day. 

An  Improvised  Pendent  Switch  (By  Roger  P.  Heller). — A  pendent 
switch  being  urgently  needed  and  none  being  at  hand,  the  writer  recently 
made  use  of  an  ordinary  key  socket  with  a  rubber  cord-bushing. 
The  insulating  collar  and  the  brass  shell  or  clamp  was  short-circuited 
by  screwing  a  copper  washer,  about  the  size  of  a  dime,  under  the 
central  screw  originally  intended  to  connect  with  the  center  stud  on  the 
lamp.  The  open  socket  was  then  plugged  with  a  cork  of  suitable  size, 
pushed  in  flush,  with  the  exposed  end  blackened  with  india-ink,  after 
which  it  was  treated  to  a  coat  of  shellac.  This  arrangement  was  found 
preferable  to  the  ordinary  push-button  pendent  switch,  as  the  latter  must 
be  steadied  by  the  fingers  or  the  other  hand,  whereas  the  improvised 
switch  requires  only  a  simple  twist  on  the  key,  the  counter-balancing 
torque  being  met  by  the  cord. 


X 
MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 

Installation,  Maintenance   of  Parts,  Testing,  Adaptation  to  Circuit 

Conditions,  Etc. 

Motors  Housed  in  External  Sheet-iron  (By  A.  T.  Todd).— The 
accompanying  Fig.  1  shows  the  unusual  but  very  successful  arrangement 
employed  in  the  installation  of  several  motors  to  drive  wood-working 
machines  in  a  box  factory  at  Pueblo,  Col.  The  motors,  aggregating  about 
40  h.p.,  are  located  in  sheet-iron  " lean-tos"  or  additions  to  the  main 
building,  all  of  the  interior  of  which  is  thus  free  for  manufacturing  opera- 
tions. Completely  inclosed  as  the  motors  are,  all  risk  of  fire  is  elimi- 
nated. Each  machine  is  belted  down  to  a  line  shaft  in  the  basement 
beneath  the  main  workroom,  and  from  this  in  turn  the  various  planers, 


Sheet  Metal 


i 

n 

LJ 
n 

FIG.     1. MOTORS  HOUSED  IN  EXTERNAL  SHEET-IRON. 

saws,  jointers,  mortisers,  etc.,  are  driven.  As  the  motors  are  on  the  main- 
floor  level,  they  can  be  reached  easily  for  inspection  or  repair.  At  the 
same  time  they  are  well  located  in  a  good  dry  place,  and  no  power  appa- 
ratus intrudes  on  the  main  floor  to  be  in  the  way  of  the  workmen. 

Installation  of  Motors  in  Dirty  Places  (By  M.  O.  Southworth). — 
Motors  in  dusty  places  generally  accumulate  an  entirely  needless  amount 
of  dust  and  dirt,  because  if  it  is  not  possible  to  give  them  complete  pro- 
tection they  generally  receive  none  at  all.  A  light  platform  or  canopy  a 
few  feet  above  the  motor  will  keep  off  perhaps  two-thirds  of  the  dust,  as 

229 


230 


HANDBOOK  OF  ELECTRICAL  METHODS 


most  of  it  settles  down  from  above;  a  barrier  a  few  feet  higher  and  a 
little  wider  than  the  motor,  raised  from  the  floor,  will  often  shield  it  from 
a  lot  more,  and  in  this  way  the  daily  cleaning,  even  in  very  dirty  places, 
will  often  be  reduced  to  a  very  small  matter.  Barriers  raised  from  the 
floor  are  especially  effective  in  wood-working  plants,  where  shavings  and 
sawdust  are  usually  projected  in  a  definite  direction  from  the  machine 
producing  them  and  can  therefore  be  easily  intercepted. 

Installing  Motors  under  Severe  Dust  Conditions  (By  N.  H.  Cicero).— 
In  installing  some  motors  in  a  stone-grinding  mill  where  fertilizer  material 
is  manufactured,  it  was  necessary  to  take  unusual  precautions  to  protect 
the  motors  against  thick  dust.  Even  induction  motors  could  not  be 
successfully  installed  in  the  same  rooms  as  the  mills  because  the  dust 
affected  the  bearings  and  lubricating  systems.  The  motors  were  there- 
fore located  in  "  doghouses"  erected  on  the  roofs  of  the  buildings  and  from 


Dust-tight 
Comp. 


Partitio  i 


Mill  Room 
FIG.    1. MOTOR  PROTECTED  FROM  DUST. 


their  pulleys  belts  were  brought  down  to  the  machines  to  be  driven. 
Each  motor  proper  was  entirely  inclosed  in  its  "  doghouse,"  a  partition 
extending  down  between  its  frame  and  the  overhanging  pulley.  The 
space  between  the  partition  and  shaft  was  then  closed  by  heavy  felt 
wipers  which  bore  on  the  shaft  and  rendered  it  impossible  for  any  dust 
to  enter  the  motor  compartment.  A  year's  experience  with  this  con- 
struction proved  its  practicability. 

A  Home-made  Iron  Switch  Box  (By  A.  G.  Trout). — An  iron  switch 
box  can  be  readily  made,  as  illustrated  on  page  231,  of  sheet  metal.  The 
box  is  bent  from  the  sheet  metal  which  is  indicated  at  development.  The 
cover  is  formed  in  the  same  way.  After  being  bent,  the  sides  are  held 
in  position  with  rivets.  Holes  are  punched  for  conductor  outlets  and 
ordinary  tubes  are  used  in  them  for  insulation.  The  switch  boxes  must 
be  painted  and  they  must  also  be  made  of  metal  not  less  than  No.  12 
U.  S.  metal  gage  (0.109  in.  thick)  to  comply  with  code  requirements. 
The  hinges  for  the  door  are  riveted  on.  Holes  are  provided  in  the  back 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


231 


for  securing  the  box  to  the  wall  and  for  supporting  the  switch  within  it 
with  stove  bolts.  There  must  be  a  space  of  at  least  1/2  in.  between  the 
walls  and  the  back  of  the  box  and  the  nearest  exposed  current-carrying 
part. 


Switch 
Base—  m 


"Tubes 
Front  View 


Wall 


\Bend  on 
-  Dotted 
Lines 


Section  Development 

FIG.    1. HOME-MADE  IRON  SWITCH  BOX. 


Design  of  Wooden  Switch-boxes  (By  Harry  Burrows). — Wooden 
switch  boxes  can  be  readily  made.  Iron  ones  are  preferable,  but  their  cost 
is  often  prohibitive.  Wooden  boxes  (Fig.  1)  should  be  of  at  least  3/4-in. 
well-seasoned  wood  and  lined  with  1/8-in.  asbestos,  secured  in  place  with 
screws  or  with  tacks  and  shellac.  Sheet  iron  of  at  least  No.  16  U.  S. 


Latch 


Hole  for  Tube 
X 


\ 


Hinges 


II 


N 


III 


Front  Elevation 


Section 


Box  \yith 

Slanting 

Top 


FIG.    1. HOME-MADE  WOODEN  SWITCH  BOX. 


metal  gage  may  be  used  instead  of  asbestos.  The  door  should  close 
against  a  rabbet  so  as  to  be  dust-tight.  Where  a  door  is  wider  than,  say, 
12  in.,  it  should  be  paneled  with  either  wood  or  1/8-in.  glass,  if  of  an  area 
not  greater  than  450  sq.  in.,  to  insure  against  distortion  due  to  warping. 
A  space  of  2  in.  should  be  allowed  between  fuses  and  the  door.  A  reliable 
catch  should  be  provided  on  the  door.  Porcelain  tubes  or  other  approved 

16 


232 


HANDBOOK  OF  ELECTRICAL  METHODS 


insulating  bushings  should  be  used  for  reinforcing  the  insulation  on  the 
wires  where  they  enter  the  box,  and  these  should  fit  the  holes  snugly. 
Where  necessary,  wires  should  be  taped  so  as  to  fill  completely  the  holes 
in  the  bushings.  Bushings  reaching  just  to  the  inside  of  the  box  should 
be  used,  as  longer  ones  will  be  broken.  It  is  recommended  that,  for 
factory  use,  the  top  of  the  box  be  slanted  as  at  III  (Fig.  1),  so  that  it  will 
not  be  used  as  a  shelf.  A  box  should  be  thoroughly  filled  and  painted 
before  it  is  lined. 

Several  switches,  either  snap  or  knife,  can  be  mounted  in  a  box  like 
that  of  Fig.  1 ;  in  fact,  it  might  be  used  as  a  panel  box.  A  box  or  cabinet 
similar  to  that  of  Fig.  2  is  often  convenient,  in  that  it  is  not  necessary  to 
open  the  door  to  manipulate  the  switch.  The  heavy  iron  wire  handle  can 


FIG.    2. ENCLOSED  WOODEN  SWITCH  BOX. 

be  attached  to  the  switch  by  bending  it  around  the  wooden  handle,  or 
the  wooden  handle  can  be  removed  and  the  wire  fastened  with  a  nut  or 
a  screw  eye.  Wooden  or  composition  cabinets  must  not  be  used  on  metal 
conduit,  armored  cable  or  metal  molding  systems.  If  the  wooden  cabinet 
is  lined  with  sheet  iron,  the  latter  must  be  painted  or  treated  in  some  way 
which  will  prevent  corrosion. 

Supporting  Motors  on  Concrete  Building  Ceilings  (By  C.  G.  Jasper). — 
Reinforced-concrete  industrial  buildings  are  now  so  common  that  the 
progressive  contractor  should  be  familiar  with  the  best  methods  of 
installing  motors  in  them.  It  is  conceded  that  the  best  location  for  a 
motor  of  a  capacity  of  less  than,  say,  50  h.p.  is  on  the  ceiling.  There  it  is 
out  of  the  way  and  does  not  occupy  floor  space.  A  good  induction  motor 
does  not  require  much  more  consideration  than  a  shafting  hanger. 

As  a  rule  motors  inverted  at  ceilings  are  held  from  stringers  of  some 
sort.  Either  timbers  (Fig.  1)  or  structural  steel  sections  (Fig.  2)  can  be 
used  for  stringers.  Wood  is  cheaper,  but  introduces  combustible  material 
in  what  might  otherwise  be  a  fireproof  installation.  Wood  also  shrinks 
and  swells.  This  results  in  loose  bolts,  vibration  and  noise.  However, 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


233 


wood  is  largely  used  because  it  can  always  be  readily  obtained  and  can 
be  erected  by  any  carpenter.  Although  somewhat  more  expensive  than 
wood,  structural  steel  members  constitute  ideal  stringers.  When  firmly 
bolted  into  place  they  stay  there.  If  an  installation  is  properly  laid  out 
it  is  not  necessary  to  drill  the  channels  or  other  sections  forming  stringers. 
They  can  be  clamped  into  place,  as  suggested  in  Fig.  2,  without  drilling. 
A  discussion  of  methods  of  mounting  motors  is  really  one  of  supporting 
stringers,  as  after  stringers  of  any  reasonable  design  are  in  place  the  motor 
bed-plate  can  be  bolted  to  them.  Either  steel  or  wooden  stringers  can 
be  supported  by  the  devices  described  herein. 


\ 


Stringers 


Yellow  Pine 
Cleat 


FIG.    1. WOODEN  STRINGERS  SUPPORTED  FROM  SPOOL  CASTING. 


Spool 
Casting 


Steel  Cbtiunela 
-,     Stringers 

Steel  Channel 


FIG.    2. STRUCTURAL  STEEL  STRINGERS   SUPPORTED   FROM   STEEL  CASTING. 

In  the  usual  concrete  building  the  ceiling  is  divided  into  bays  by 
beams  that  extend  down  from  its  surface.  Stringers  are  most  often 
supported  from  the  beams,  as  suggested  in  the  illustrations,  but  are 
sometimes  clamped  to  the  floor  slabs  between  beams.  The  initial  step, 
then,  in  erecting  a  stringer  is  to  arrange  some  method  of  attaching  to  the 
beams  the  bolts  that  are  to  support  it.  If  foresight  has  been  exercised, 
provision  for  supporting  bolts  will  have  been  made  during  the  erection  of 
the  building.  Otherwise  the  installer  must  drill  holes  in  the  concrete  to 
accommodate  the  bolts. 

Figs.  3  and  4  show  methods  of  attaching  bolts  to  beams  of  concrete 


234 


HANDBOOK  OF  ELECTRICAL  METHODS 


buildings  wherein  no  provision  for  bolts  was  made  at  the  time  the  building 
was  erected.  It  should  be  noted  that  in  both  of  these  examples  3/4-in. 
round  stock  is  used  for  the  holes.  Bolts  of  smaller  diameter  are  not 


''•'""•'•  •'•.':  «'51::.f 

111 

K-W-l 

34    Eye  Bolt 

::<31v'-"-I  •"'••"  p: 

Yellow  Pine 
Stringer 


FIG.    3. EYE-BOLT  SUPPORTING  STRINGERS. 


trustworthy  for  supporting  the  loads  ordinarily  encountered  in  practice; 
also  there  is  a  possibility  of  a  bolt  smaller  than  3/4  in.  diameter  being 
twisted  asunder  when  a  nut  is  tightened  with  a  wrench  in  the  hands  of  an 


Floor 


/HI 

/  ^F  ~t^p^Washer 

3x6  Yellow  Pine  Stringers 

FIG.    4. HOOK-BOLTS  SUPPORTING  STRINGERS. 

able-bodied  wireman.  In  Fig.  3  a  horizontal  hole  is  drilled  through  the 
beam  and  through  it  is  passed  an  ordinary  bolt  which  supports  an  eye- 
bolt  on  either  side  of  the  beam.  The  eye-bolts  support  the  stringers. 


Casting" 


FIG.    5. SPOOL  CASTINGS  IN  CEILING. 


Where  one  bolt  will  safely  sustain  the  load  an  L-bolt,  similar  to  that  shown 
in  Fig.  7,  can  be  used  instead  of  the  through  bolt  and  the  two  eye-bolts. 
In  Fig.  4  slanting  holes  are  drilled  in  the  beam  side,  in  which  hook-bolts 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


235 


engage.  The  hook-bolts  are  merely  pieces  of  round  stock  threaded  on  one 
end  and  provided  with  a  nut  and  bent  to  an  angle  of  about  60  deg.  to  form 
a  hook  at  the  other. 

In  drilling  holes  in  concrete  an  air  drill  or  an  electric  drill  will  be  found 
profitable  if  there  is  much  drilling  to  be  done.     If  such  an  investment  is 

a  • 

,     i 

r< 1% — >\      i 


c 


Tap  for   5/&  Bolt 
FIG.    6.  -  DETAILS  OF  SPOOL  CASTING. 

not  justified,  the  ordinary  rock  drill  (Fig.  8),  which  resembles  a  cold  chisel 
except  that  it  is  longer  and  has  a  greater  angle  between  faces  at  its  cutting 
edge,  is  the  best  tool  to  use.  Such  a  drill  can  be  readily  forged  from  tool- 
steel  stock  by  a  blacksmith  and  so  tempered  as  to  maintain  its  cutting 
edge  for  a  maximum  period.  Note  (Fig.  8)  that  the  cutting  edge  of  the 
drill  is  forged  slightly  wider  than  the  stem  to  provide  clearance.  In 


1 


(n> 


3x6  Yellow  Pine 
Stringers 

FIG.    7. L-BOLT  IN  TIN  TUBE  HOLE. 

using  the  drill  its  head  is  pounded  with  a  hammer  and  the  drill  is  turned  a 
portion  of  a  revolution  between  each  blow  to  make  the  hole  cylindrical 
and  to  prevent  the  drill  from  wedging  in  it. 

In  modern  concrete  industrial  buildings,  as  above  suggested,  some 
provision  is  usually  made  during  construction  so  that  pipes  for  heating  and 
sprinkler  systems,  shafting  stringers  and  electrical  conduits  can  be  sup- 
ported without  its  being  necessary  to  drill  the  concrete  after  the  building 
is  completed.  One  method  of  making  such  provision  is  to  cast  in  the  con- 
crete ceilings,  as  shown  in  Fig.  5,  cast-iron  spools  such  as  that  detailed  in 


236 


HANDBOOK  OF  ELECTRICAL  METHODS 


Fig.  6.  Where  these  spools  are  inserted  stringers  can  be  bolted  to  them, 
as  shown  in  Figs.  1  and  2.  These  illustrations  show  the  spools  set  in 
beams  instead  of  in  floor  slabs.  For  stringers  the  beam  location  is  pref- 
erable because  with  it  an  unbroken  line  of  stringers  can  be  erected  the 
entire  length  of  a  building.  Cutting  of  the  stringers  into  lengths  to  fit  the 
spaces  between  beams  is  avoided. 


Round  Off 


Clearance 


Side  Elevation 


o 

Head 
End  View 


Cutting  Edge 
Rounding  not  Square 


Section 
FIG.    8. DRILL  FOR  CONCRETE. 


Fig.  7  illustrates  another  method  of  preparing  concrete  beams  for  the 
reception  of  bolts.  A  sheet-iron  tube  is  cast  in  the  concrete  at  each 
location  where  a  support  point  is  desired;  then  the  stringers  to  support  a 
motor  can  be  held  by  either  an  L-bolt  (Fig.  7)  or  a  through  bolt  and  two 
eye-bolts,  as  in  Fig.  3. 

Repairing  a  Broken  Motor  Leg  (By  James  F.  Hobart). — During  ship- 
ment the  foot  of  a*30-hp.  induction  motor  became  broken  as  shown  in 


FIG.    1. BREAK  IN  MOTOR  FRAME. 

Fig.  1.  It  was  necessary  to  repair  the  break  with  the  least  possible  delay 
and  at  the  lowest  cost.  The  foot  being  an  isolated  projecting  member  of 
considerable  section,  it  was  not  necessary  to  provide  for  the  expansion 
and  contraction  of  other  portions  of  the  casting.  The  sole  object  was 
to  heat  the  fracture  without  damaging  the  coils  of  the  stator  winding. 
The  outside  of  the  motor  casing  is  shown  at  A;  B  and  C  are  the  feet, 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC.  237 

and  the  break  to  be  repaired  is  visible  at  D.  The  field  winding  E  was 
protected  by  placing  between  the  coils  and  the  shell  casting  several  thick- 
nesses of  asbestos  board  which  had  previously  been  saturated  with  water. 
The  several  layers  of  asbestos  which  were  packed  into  the  space  between 
the  shell  and  the  field  winding  are  shown  at  F.  The  pieces  were  held  in 
position  by  several  small  wooden  wedges  which  were  driven  between  the 
asbestos  board  and  casing. 

When  the  first  attempt  at  welding  was  made  excessive  caution  pre- 
vented adequate  heating  of  the  fractured  parts,  and  only  the  surface  of 
the  break  was  welded.  This  weld  was  very  promptly  broken  as  soon  as 
strain  was  placed  upon  the  foot  again. 

The  owner  of  the  motor  was  told  that  a  second  attempt  would  not  be 
made  unless  the  motor  foot  could  be  treated  exactly  as  though  it  were  a 
bare  casting  with  no  windings  in  proximity  to  it.  He  assented  but  sta- 
tioned one  of  his  men  beside  the  motor  to  inspect  the  field  winding  during 
the  operation. 

When  the  motor  was  in  position  above  the  forge,  bricks  were  placed 
about  the  broken  parts  to  keep  the  heat  as  much  as  possible  from  all 
other  portions  of  shell.  Pieces  of  asbestos  board  were  freely  used.  After 
these  precautions  had  been  taken  the  foot  was  heated  to  a  red  heat.  The 
welding  was  then  completed  as  speedily  as  was  possible.  The  asbestos 
apparently  did  its  work  well,  for  the  coils  were  not  damaged  and  the  motor 
was  placed  in  service. 

Electric  Welding  of  Broken  Motor  Shaft  (By  A.  T.  Sartoris) .— The 
accompanying  Fig.  1.  makes  clear  a  method  of  welding  broken  motor 


cr_~_^ 


Jroken 


Shaft 


i^'-in.  Pin  ^Turned  Flush 

FIG.    1. WELDING  A  BROKEN    SHAFT. 

shafts  which  has  been  in  use  at  one  plant  for  several  years  and  results  in 
a  repair  that  is  practically  as  strong  as  the  original  shaft.  The  broken 
section  is  first  shaved  off  square  and  a  hole  drilled  in  the  center  to  take  a 
1/2-in.  steel  pin.  The  shaft  extension  is  meanwhile  cut  to  proper  length, 
allowing  for  the  1/2-in.  kerf  which  is  to  be  filled  up  with  metal  flowed  on 
in  making  the  weld.  After  the  extension  has  been  drilled  the  two  parts 
are  joined  by  the  pin  as  shown,  and  with  an  electric  arc  additional  metal 
is  added  around  the  joint  until  the  shaft  diameter  is  slightly  exceeded. 
After  making  sure  that  a  true  weld  has  resulted,  the  surplus  can  be  turned 
down,  removing  all  traces  of  the  repair. 


238 


HANDBOOK  OF  ELECTRICAL  METHODS 


Rebabbitting  Motor  Bearings  (By  C.  R.  McGahey). — The  continuous 
operation  of  motors  and  generators  depends  very  largely  upon  the  care 
bestowed  upon  them,  and  this  is  especially  so  of  small  motors.  Many 
of  the  latter  are  thrown  out  of  commission  because  of  lack  of  attendance 
or  for  the  want  of  proper  setting.  This  is  not  only  true  of  direct-current 
motors,  but  also  of  alternating-current  motors,  the  general  impression 


FIG.    1. SOLID    BEARING. 

being  that  the  latter  require  no  care  whatsoever.  Where  induction 
motors  of  the  squirrel-cage  type  are  set  on  some  pieces  of  timber  or  on  a 
vibrating  foundation  the  vibration  will  cause  the  insulation  to  work  out 
much  more  quickly  and  proper  service  thereafter  is  impossible.  A  good 
foundation  is  very  essential  for  the  reliable  operation  of  motors.  The 
care  of  bearings  is  also  another  important  consideration,  and  the  mere 


FIG.    2. RENEWABLE  BEARING. 

fact  that  a  motor  bearing  is  working  well  to-day  does  not  mean  that  it 
will  be  in  the  same  working  condition  an  hour  hence.  It  is  advisable 
where  motors  are  used  very  much  to  carry  a  separate  set  of  bearings  in 
stock  for  each  size  of  motor  in  operation,  so  that  when  the  babbitt  is  melted 
or  becomes  loose  it  may  be  replaced  without  the  necessity  of  shutting 
down  the  motor  for  any  considerable  length  of  time.  Some  motor 


a 


FIGS.    3  AND  4. BEARING  JIG  AND  ARBOR. 


bearings  have  an  iron  shell  lined  with  babbitt  metal  which  is  poured  in 
place,  while  others  have  a  finished  babbitt  liner.  Fig.  1  shows  a  bearing 
of  the  former  type,  and  such  are  very  difficult  to  repair,  especially  if  ring 
oilers  are  used.  Fig.  2  shows  a  bearing  in  which  the  babbitt  is  merely 
slipped  into  place.  A  jig  for  rebabbitting  bearings  is  shown  in  Fig.  3. 
This  consists  of  a  plate  M  on  top  of  which  is  a  yoke  piece  F  bored  out  to 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


239 


fit  the  bearing  surface  U  (Fig.  1).  An  arbor  X  represents  the  diameter  of 
the  motor  shaft.  The  distances  C  and  D  must  be  accurate,  so  that  the 
bearing  will  fit  when  placed  in  the  motor.  The  pins  E  serve  to  hold  the 
housing  in  place  while  the  babbitt  metal  is  poured.  In  the  engraving, 
Fig.  3,  the  babbitt  metal  is  represented  at  B  and  a  side  view  of  the  arbor 
is  shown  in  Fig.  4.  The  latter  shows  the  projecting  rings  to  form  the  oil 
grooves.  A  jig  of  this  kind  will  be  found  very  useful  for  repairing  separate 
motor  bearings  and  a  bearing  such  as  that  shown  in  Fig.  1  can  also  be 
repaired  in  this  way,  as  the  fitting  forms  the  guide  for  the  centering  of  the 
shell  for  the  babbitt  metal.  Great  care  must  be  taken  in  the  construction 
of  the  jig  so  that  the  babbitt  lining  will  be  true,  otherwise  it  will  not  fit 
the  shaft  and  will  run  hot. 

Care  of  Electric  Motors  (By  Wm.  Kavanagh). — A  good  bellows  will  be 
found  a  very  useful  tool  in  keeping  motors  clean.  Where  several  motors 
are  in  daily  use  an  air  line  should  be  situated  close  to  each  motor,  the 
line  having  a  hose  connection  and  stopcock  handily  located,  for  the 


FIG.    1. MANDREL  FOR  SHAPING  OILING  RINGS. 

purpose  of  blowing  off  the  accumulated  dust  around  the  fields,  armature 
and  brush  connections.  Air  at  high  pressure  should  not  be  used  because 
it  is  likely  to  fray  the  insulation  or  possibly  blow  it  away  entirely.  A 
pressure  varying  from  5  Ib.  to  10  Ib.  per  square  meter  will  be  found 
sufficiently  strong  to  blow  off  the  dust  and  baked  material,  thus  removing 
the  liability  of  fire. 

Whenever  the  oiling  rings  are  out  of  true  they  will  not  rotate,  thus 
causing  a  heated  journal  or  bearing.  Occasionally  when  oiling  rings  are 
being  put  in  place  they  become  dented  or  pressed  out  of  "true,"  and  of 
course  when  this  occurs  the  rings  must  be  pressed  or  hammered  back 
to  shape.  A  very  handy  tool  enabling  the  rapid  shaping  of  the  rings  is 
shown  in  Fig.  1.  This  is  a  tapered  mandrel  made  out  of  a  piece  of  hard 
wood  or  iron,  the  small  end  of  the  mandrel  suiting  rings  having  the 
smallest  diameter,  while  rings  of  large  size  can  be  shaped  on  the  larger 
end,  as  shown  at  RRR. 

Fig.  2  illustrates  another  very  handy  tool,  known  as  a  "  sandpaper 
block."  Sometimes  it  is  desirable  to  use  a  strip  of  sandpaper  on  the 
commutator  to  clean  off  foreign  matter.  With  small  motors  it  is  some- 
times difficult  to  do  this,  but  by  employing  the  sandpaper  block  as  shown 


240  HANDBOOK  OF  ELECTRICAL  METHODS 

it  is  a  simple  matter  to  clean  any  size  of  commutator  effectively  and  with- 
out incurring  the  danger  of  shock.  The  block  can  be  made  of  any  size 
required  and  by  wrapping  the  curved  end  with  one  or  more  strips  of  sand- 
paper the  commutator  can  be  cleaned  as  often  as  necessary.  The  sand- 
papei  may  be  held  in  position  by  means  of  a  few  thumb-tacks,  and  when 
worn  it  is  easily  removed  and  a  new  strip  put  in  its  place.  It  will  be 
found  advantageous  to  line  the  curved  end  of  the  block  with  a  piece  of 


FIG.    2. " SANDPAPER  BLOCK5'  FOR  CLEANING  COMMUTATORS. 

felt  or  thick  cloth  over  which  the  sandpaper  can  be  placed,  the  object 
being  to  have  the  sandpaper  conform  more  closely  to  the  shape  of  the 
commutator.  Thus  a  slight  pressure  of  the  hand  is  all  that  is  required  to 
clean  the  commutator  thoroughly.  If  possible,  the  curve  of  the  block 
should  always  suit  the  curve  of  the  commutator;  when  such  is  the  case 
the  entire  surface  of  the  commutator  will  receive  an  equal  amount  of 
sandpapering,  which  tends  to  maintain  a  true  surface.  When  the  brushes 
are  not  staggered  the  commutator  tends  to  wear  unevenly,  but  the  correct 
use  of  this  sandpaper  block  will  offset  the  tendency  almost  entirely. 


FIG.    3. APPLICATION  OF  "SANDPAPER  BLOCK." 

Fig.  3  shows  the  application  of  this  block  to  a  commutator  and  illustrates 
how  convenient  it  becomes  for  motors  situated  on  ceilings  or  in  other 
inaccessible  places. 

Troubles  with  Induction  Motors  (By  C.  R.  McGahey). — Motors 
are  frequently  installed  in  manufacturing  plants  in  such  manner  as  to 
cause  considerable  trouble  and  annoyance,  not  to  mention  frequent 
shut-downs.  Sometimes  one  finds  an  induction  type  of  motor  having  a 
squirrel-cage  rotor  coupled  so  that  it  will  be  necessary  for  it  to  start  under 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


241 


heavy  load.  Aside  from  the  injurious  action  of  the  excessive  current  upon 
the  motor  itself,  this  method  of  running  an  induction  motor  is  detrimental 
to  the  life  of  the  belt  and  the  starting  box,  and  causes  much  annoyance  by 
the  opening  of  circuit-breakers  and  the  blowing  of  fuses.  For  instance,  in 
the  case  of  motors  driving  heavy  shearing  machinery,  punches  or  devices 
carrying  heavy  balance  wheels,  these  should  first  be  placed  into  operation 
without  load,  so  that  the  stored  energy  in  the  flywheels  may  be  utilized 
when  the  load  is  thrown  on.  To  start  such  machinery  on  the  jump 
requires  an  excessive  amount  of  energy  and  current  oftentimes  greater 
than  that  permitted  by  the  insurance  authorities  for  the  size  of  wire  used 
in  feeding  the  motor.  Many  of  these  installations  can  be  made  to  operate 
more  satisfactorily,  and  require  less  energy  at  starting,  by  arranging  the 
motor  drive  as  shown  in  Fig.  1.  Here  a  friction  clutch  is  employed  on 
the  main  lineshaft  so  that  the  motor  may  be  brought  up  to  speed  before 


Friction  Clutch 


ft  n 


n 


FIGS.    1  AND  2. TROUBLES  WITH  INDUCTION  MOTORS. 

it  is  connected  to  the  load.  The  friction  clutch  permits  the  load  to  be 
picked  up  gradually  while  the  motor  is  running  at  full  speed.  In  selecting 
a  friction  clutch  one  should  be  certain  that  it  possesses  ample  capacity. 
Not  infrequently  a  clutch  which  has  ample  capacity  at  first  will  not  carry 
its  connected  load  after  long  service,  so  that  it  is  best  to  purchase  one 
slightly  larger  than  would  be  absolutely  necessary.  It  will  then  be  found 
to  require  very  little  attention  and  give  much  better  service  than  one  oper- 
ating up  to  its  limit.  The  main  feature  which  a  friction  clutch  used  in 
connection  with  an  electric  motor  should  possess  is  ample  sleeve  bearing, 
so  that  it  will  remain  true  and  give  a  good  contact  without  slippage.  It 
is  felt  that  if  the  suggestions  above  are  heeded  burn-outs  at  contact  points 
in  the  starting  box,  such  as  shown  in  Fig.  2  at  C  and  E,  will  be  entirely 
avoided.  The  extra  current  which  is  required  in  a  motor  of  the  induction 


242  HANDBOOK  OF  ELECTRICAL  METHODS 

type  starting  under  full  load  from  standstill  is  exceedingly  detrimental  to 
the  life  of  contact  points,  regardless  of  the  oil,  and  it  is  not  long  before 
trouble  is  experienced  with  the  starting  box.  Unfortunately,  owing  to 
the  simplicity  of  the  induction  motor,  it  is  frequently  run  under  unfair 
conditions,  the  most  prevalent  of  which  is  that  of  throwing  the  motor  on 
the  line  under  load. 

Starting  Torque  of  Induction  Motors  (By  M.  O.  Southworth). — 
Probably  the  most  common  mistake  in  the  installation  of  induction 
motors  is  the  selection  of  a  motor  that  is  too  small  to  start  the  load.  Most 
machinery  manufacturers  can  now  give  us  fairly  reliable  data  as  to  the 
power  required  to  drive  their  machinery  under  running  conditions,  but 
few  of  them  know  what  starting  torque  is  required  to  start  the  load  from 
rest  and  bring  it  up  to  speed.  Some  classes  of  machinery,  such  as  fans  and 
centrifugal  pumps,  require  little  effort  at  starting,  but  the  load  accumu- 
lates as  the  speed  increases — other  classes  of  machinery  require  practi- 
cally the  same  effort  at  starting  that  they  do  to  maintain  their  speed  after 
in  motion  and  some  even  more  than  this.  In  the  latter  class  are  pumps 
and  air  compressors  starting  under  pressure.  Elevators  and  hoists  or 
other  machinery  that  move  a  dead  weight  or  pull  against  a  fixed  constant 
resistance  and  often  a  line  shaft  with  many  idle  belts  will  be  found  to 
belong  to  the  class  that  requires  more  effort  at  starting  than  after  it  is  in 
motion  and  driving  full  load. 

This  is  often  the  controlling  feature  in  selecting  a  suitable  induction 
motor,  for  while  modern  motors  will  exert  a  starting  effort  considerably 
greater  than  that  corresponding  to  their  rated  horse-power,  they  are  often 
found  connected  to  loads  that  they  will  run  easily  after  starting,  but  will 
fail  to  start  without  assistance.  Very  often  this  is  due  to  a  drop  in  volt- 
age at  the  motor  terminals  on  account  of  insufficient  transformer  equip- 
ment or  a  long  supply  circuit  of  insufficient  size.  This  condition  is  readily 
discovered  by  a  voltmeter,  but  even  then  the  question  often  arises  as  to 
whether  the  motor  is  large  enough  if  the  voltage  were  properly  maintained 
or  how  large  a  motor  should  be  used.  The  positive  determination  of  this 
matter  is  so  simple  that  it  is  surprising  the  subject  is  so  often  a  matter 
of  controversy.  The  method  of  procedure  in  typical  cases  given  below  is 
presented  in  the  hope  that  resort  to  these  simple  and  convincing  tests  will 
in  a  measure  eliminate  the  fruitless  argument  that  often  results  in  such 
cases.  Suppose  an  induction  motor  is  belted  to  a  line  shaft  which  may 
drive  a  group  of  machines  or  a  single  machine  through  other  belts,  as 
shown  in  Fig.  1  It  is  found  that  the  motor  fails  to  start  this  load  and  the 
question  arises  whether  the  load  is  greater  than  the  motor  should  be 
expected  to  start  or  whether  the  motor  is  at  fault.  The  driven  machinery 
may  be  connected  or  not,  but  with  this  we  are  not  concerned,  as  it  is  the 
actual  torque  that  the  motor  has  to  exert  under  starting  conditions  that 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC.  243 

is  to  be  the  subject  of  test.  There  is  always  some  slack  in  the  connecting 
belts  and  when  the  motor  is  started  it  first  turns  the  line  shaft  slightly,  tak- 
ing up  this  slack,  and  then  the  full  starting  effort  necessary  to  overcome  the 
resistance  of  the  belts  and  the  idle  pulleys  will  be  required. 

If  the  pounds  pull  the  driving  belt  has  to  exert  to  start  this  shaft 
and  machinery  can  be  found  this  can  easily  be  translated  into  horse-power 
by  considering  it  in  connection  with  the  belt  speed  after  the  motor  is 
running,  and  to  find  this  pull  one  can  proceed  as  indicated  in  Fig.  1.  A 
clamp  which  may  be  made  of  two  pieces  of  hard  wood  slightly  wider  than 


FIG.    1. DETERMINING  BELT  PULL. 

the  belt,  with  bolts  passing  through  each  end,  is  fastened  to  the  pulling 
side  of  the  belt  and  by  means  of  a  rope  fastened  in  a  loop  around  the  belt 
back  of  this  clamp  or  otherwise  attached  to  the  clamp  an  ordinary  spring 
balance  is  fastened  to  the  belt,  as  shown  in  Fig.  1.  In  the  case  of  a  small 
motor,  the  clamp  may  often  be  omitted  and  the  rope  simply  tied  around 
the  belt.  Now,  holding  this  balance  parallel  to  the  belt  and  pulling  in 
the  direction  that  the  belt  runs,  first  take  up  the  slack  of  the  driving 
belts  and  then  a  further  pull  will  start  the  shaft  and  the  maximum  reading 
of  the  scale  will  indicate  the  number  of  pounds  of  useful  belt  pull  required 
to  start  the  load.  From  the  number  of  revolutions  and  the  size  of  the 
pulleys  we  find  the  belt  speed  in  feet  per  minute  and  multiplying  this  by 
the  pounds  pull,  we  have  the  number  of  foot-pounds  per  minute,  which, 
divided  by  33,000,  give  us  the  horse-power  of  the  motor  which  will  exert 
this  starting  effort  without  overload.  For  example:  Suppose  a  pull  of 
60  Ib.  is  registered  on  the  spring  balance  and  the  driven  pulley  on  the 
line  shaft  is  36  in.,  or  3  ft.,  in  diameter,  and  runs  at  200  r.p.m.,  the  horse- 
power would  be:  H.p.  =  60X3X3.14X200-^33,000  =  3.12. 

Most  modern  motors  will  exert  a  starting  torque  about  50  per  cent, 
greater  than  the  torque  corresponding  to  their  full  rated  load  when  full 


244 


HANDBOOK  OF  ELECTRICAL  METHODS 


voltage  is  impressed  at  their  terminals,  but  it  is  often  undesirable  to  apply 
full  voltage  on  account  of  the  heavy  current  that  will  be  drawn  from  the 
line.  Hence  this  excess  should  be  used  only  as  a  margin  for  emergencies. 
With  large  motors  it  is  better  practice  to  arrange  the  load  so  that  it  may 
be  disconnected  at  the  start  and  not  over  30  per  cent,  to  50  per  cent,  of 
full-load  synchronous  torque  be  required. 

In  Fig.  2  is  shown  the  method  for  testing  a  motor  directly  connected 
to  an  elevator  or  other  machine  that  may  be  driven  by  a  coupling.  A  bar 
of  iron  or  wood  of  convenient  length  is  clamped  beneath  the  heads  of  the 
coupling  bolts  or  may  be  simply  hooked  in  place  between  the  bolts  and 
shaft  in  such  a  way  that  it  serves  to  move  the  motor  and  driven  machine 
in  the  normal  direction.  The  motor  is  turned  until  all  the  backlash  is 
taken  out  and  it  actually  begins  to  raise  the  load,  then  a  spring  balance  is 
applied  at  a  fixed  distance  "L"  from  the  center  of  the  shaft  and  the  pull 
on  the  balance  would  indicate  the  effort  required  to  start  the  load  as  in  the 


rV 


FIG.    2. TESTING  MOTOR. 


case  of  the  belt.  Care  must  be  taken  to  pull  in  a  direction  at  right  angles 
to  the  line  from  the  center  of  the  shaft  to  the  point  where  the  balance  is 
attached  to  the  lever  and  to  measure  the  distance  from  the  center  of  the 
shaft  to  that  point.  Then  the  horse-power  is  obtained  by  the  formula: 
H.p.  =6.28  N.L.P.-^  33,000  in  which  P  equals  number  of  pounds  pull 
shown  by  the  balance,  L  the  distance  from  the  center  of  shaft  to  the  bal- 
ance, in  feet,  and  N  the  number  of  revolutions  of  the  motor  per  minute. 
In  the  case  of  a  pump  or  other  machine  driven  by  gearing,  the  spring 
balance  may  be  attached  to  the  rim  of  the  gear  and  pulled  in  a  tangential 
direction,  and  the  horse-power  obtained  by  multiplying  the  pull  by  the 
speed  of  the  gear  in  feet  per  minute  and  dividing  by  33,000.  This  test 
may  also  be  used  to  determine  in  advance  the  horse-power  required  to 
drive  an  elevator  or  similar  machine  before  the  installation  of  a  motor. 
It  is,  of  course,  not  applicable  for  this  purpose  when  the  load  is  of  such 
character  that  the  torque  increases  with  the  speed,  but  is  perfectly  reliable 
and  accurate  in  all  cases  for  determining  the  starting  effort. 

Turning  down  a  Commutator  (By  J.  Cloyd  Downs). — The  following 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC.  245 

scheme  for  turning  down  a  commutator  may  be  new  to  some  and  has 
been  used  in  a  number  of  instances  with  very  satisfactory  results.  The 
method  usually  used  to  turn  down  a  commutator  on  a  repair  job  where  the 
armature  is  too  large  to  remove  is  to  leave  one  or  two  pairs  of  brush  arms 
on  and  run  the  machine  from  these  at  as  low  a  speed  as  the  field  regulation 
will  permit,  or  possibly  with  a  water  rheostat  in  the  armature  circuit. 
Of  course,  this  will  do  where  nothing  else  is  possible,  but  there  is  always 
bad  sparking  and  burning  at  the  point  of  the  cutting  tool  due  to  its  short- 
circuiting  the  bars  when  it  crosses  the  mica.  The  tool  has  to  be  sharpened 
frequently  and  the  job  is  seldom  good  even  where  the  greatest  care  is 
exercised.  For  this  reason  it  is  always  best  to  belt  the  machine  to  a 
separate  motor  and'turn  down  the  commutator  with  the  fields  unexcited. 
In  the  plant  with  which  the  writer  is  connected  there  are  several  machines 


FIG.    1. TURNING  DOWN  A  COMMUTATOR. 


set  symmetrically  with  their  shafts  parallel.  The  shafts  overhang  the 
outside  of  the  bearings  sufficiently  to  enable  one  to  put  a  pulley  on  the 
shaft  of  the  machine  to  be  repaired.  The  belt  is  then  put  directly  on  the 
shaft  of  the  other  machine  and  by  using  a  suitable  pulley  the  proper  speed 
for  turning  down  is  obtained.  A  commutator  20  in.  or  slightly  more  in 
diameter  can  be  run  at  about  75  r.p.m.  with  good  results,  but  it  is  better 
to  keep  below  this  speed  than  to  exceed  it.  The  accompanying  Fig.  1 
shows  this  scheme  very  plainly.  It  is  unnecessary,  of  course,  to  shut 
down  the  machine  used  as  the  motor  and  the  additional  load  would  seldom 
if  ever,  be  of  serious  moment. 

Adjusting  Interpole  Fields  of  Generator  (By  H.  M.  Nichols). — The 
following  method  of  adjusting  the  interpole  fields  of  generators  may  be  of 
interest  to  those  who  operate  this  class  of  apparatus.  First  set  the  brushes 
on  no  load  neutral  by  taking  voltage  readings  with  the  armature  rotating 
clockwise  and  then  counter-clockwise.  The  brushes  will  be  on  the  neutral 
point  when  the  two  voltage  readings  are  the  same.  Then  throw  the  rated 
load  on  the  generator  and  adjust  the  interpole  field  strength  until  the 
neutral  point  is  brought  back  to  the  no-load  neutral  position,  this  being 
determined  by  taking  voltage  readings  with  the  generator  rotating  in 
both  directions.  The  interpole  field  strength  is  now  properly  adjusted 


246 


HANDBOOK  OF  ELECTRICAL  METHODS 


for  all  loads  up  to  the  saturation  of  the  interpoles  and  a  permanent  shunt 
of  German  silver  should  be  made  up  for  the  interpole  field  winding. 

Wiring  Equipment  for  Motor  Testing  (By  H.  S.  Travis). — It  is  often 
desirable  to  test  motors  that  are  already  installed  in  order  to  ascertain  the 
power  required  for  certain  operations  or  to  find  whether  a  larger  or  smaller 
one  than  the  one  operating  will  best  satisfy  the  existing  conditions.  In 
making  such  tests  usually  the  most  expensive  and  tedious  portion  of  the 
work  is  to  connect  the  measuring  instruments  into  the  motor  circuit.  This 
is  particularly  true  where  the  motor  is  one  of  large  capacity  having  large 
conductors.  If  motors  are  tested  frequently  both  time  and  money  are 
saved  by  the  use  of  portable  wiring  equipment  by  means  of  which  testing 
instruments  can  be  quickly  and  effectively  inserted  in  the  motor  circuits. 


Dummy  Fuse 
Connector 


Motor 
Under 
.Test" 

FIG.    1. CONNECTIONS  FOR  MOTOR  TESTING. 

Fig.  1  shows  the  application  of  such  a  device.  With  it  instruments 
can  be  connected  into  the  motor  circuits  without  disturbing  the  perma- 
nent wiring.  In  the  engraving  a  direct-current  motor  is  shown,  but  the 
scheme  is  quite  applicable  to  three-phase  motors.  Two  dummy  fuse 
connectors  will  be  required  for  three-phase  testing,  whereas  only  one  is 
required  in  direct-current  tests.  Referring  to  Fig.  1 :  Instead  of  discon- 
necting one  of  the  leads  to  the  motor  in  order  to  cut  in  the  series  coils  of 
the  wattmeter,  the  connection  is  arranged  at  the  fusible  cut-out.  Nearly 
all  motors  are  protected  with  a  cut-out  of  this  type.  One  of  the  fuses  is 
removed  from  the  cut-out  and  in  its  stead  is  inserted  a  dummy-fuse-con- 
nector like  that  detailed  in  Fig.  2.  The  leads  to  the  wattmeter  are  con- 
nected— frequently  permanently — to  the  binding  posts  of  the  connector. 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


247 


There  is  no  path  directly  through  the  connector  because  the  old  fuse  from 
which  it  is  made  has  been  taken  apart  and  all  portions  of  the  fusible  con- 
ductor that  it  contained  have  been  removed.  The  circuit  to  the  motor 
must,  therefore,  be  completed  through  the  wattmeter. 

The  details  of  Fig.  2  show  how  the  connector  is  made.  Connecting 
straps  (see  Fig.  3)  are  soldered  to  the  ferrules  of  what  was  the  fuse.  The 
terminals  are  arranged  by  soldering  on  each  connecting  strap  a  nut  (see 
Figs.  2  and  3)  into  which  a  brass  machine  screw  turns.  Wattmeter  leads 


lade/ 


Series  Leads 
Fibre  Tube 


Shunt 


d 

/Brass 
^Ferrule 


Brass  Machine 
Screw 


Nut 


TJ4 


Brass  connecting 
Strap  soldered  on 


FIG.    2.  -  CONNECTING  STRAPS  ON  101-200  AMP.  FUSE. 


are  either  permanently  clamped  under  the  heads  of  the  brass  machine 
screws  or  soldered  into  lugs  of  the  form  shown  in  Fig.  4.  The  nut 
should  preferably  be  of  brass,  as  it  can  be  soldered  more  easily;  but  an  iron 
nut  will  do.  In  soldering  iron  the  metal  must  first  be  filed  so  that  a  clean, 
new  surface  will  be  presented  and  then  tinned,  using  ammonium  chloride 
(sal-ammoniac)  —  in  crystalline  or  powdered  form  —  as  a  flux,  before  an 
attempt  is  made  to  solder  it  to  another  metal.  After  the  straps  are  affixed 
to  the  ferrules  of  the  old  fuse  a  hole  for  a  small  machine  screw  is  drilled 


Drill  hole  through 
Ring  I/is  larger 
than  diamete: 
of  machine 
screw. 


Make  large 
-enough  to 
J_  admit  stove 
bolt  nut. 

Drill  ancf 

tap  for 

voltmeter 

screw  after 

ring  is 

soldered 

to  fuse,  • 


Nut  soldered  on 


Brass 

Machine 

Screw 


FIG.    3.- 


width  of 

ferrule 

minus  1 


-DETAILS  OF  CONNECTING 
STRAP. 


FIG.  4. LUGS  FOR 

CURRENT  LEADS. 


and  tapped  in  one  of  them,  as  indicated  in  Fig.  2.  This  provides  means  for 
connecting  one  of  the  voltage  leads  to  the  wattmeter.  Although  Fig.  2 
only  shows  a  connector  for  101-200-amp.  National  Electrical  Code  fuse 
holders,  connectors  for  the  other  size  code  holders  can  be  arranged  in 
essentially  the  same  way.  All  of  the  directions  given  on  Fig.  3  are  general 
and  apply  to  all  sizes  of  knife-blade  contact  fuses. 

Where  connectors  are  to  be  made  from  ferrule  contact  fuses — those 

17 


248 


HANDBOOK  OF  ELECTRICAL  METHODS 


of  capacities  under  61  amp. — it  is  best  to  solder  the  wattmeter  leads 
directly  to  the  ferrules.  Conductors  necessary  for  the  relatively  small 
currents  involved  will  be  so  small  that  they  will  not  be  difficult  to  handle 
and  there  would  be  no  advantage  in  being  able  to  disconnect  them  at  the 
ferrules. 

The  lug  shown  in  Fig.  4,  which  may  be  used  on  the  dummy-fuse-con- 
nector ends  of  the  wattmeter  leads,  is  made  from  an  ordinary  lug  by  filing 
out  the  portion  enclosed  within  the  dotted  lines  in  the  figure.  The  advan- 
tage of  this  type  of  "  forked  "  lug  is  that  it  may  be  inserted  under  a  machine 
screw  head  on  the  connector,  without  removing  the  screw  entirely  from 
its  hole.  Time  is  thus  saved  and  the  possibility  of  the  screw  becoming 
lost  is  avoided. 

Referring  again  to  Fig.  1:  A  portable  fuse  is  often  inserted  in  the 
circuit  leg  that  contains  the  dummy-fuse-connector  so  that  the  motor  and 
instruments  will  be  protected  while  the  test  is  being  made.  Such  a  fuse 
is  not  always  cut  in;  it  is,  however,  safer  to  do  so. 

Provision  is  made  on  the  connector  for  the  attachment  of  one  voltmeter 
lead.  The  other  lead  can  be  connected  to  its  side  of  the  circuit  by  insert- 
ing its  thin  metal  terminal  lug  or  its  bared  end  between  the  fuse  knife- 
blade  and  the  corresponding  contact  clip. 

Testing  Polarity  of  Field  Coils  (By  E.  R.  Shepard).— In  testing  the 
polarity  of  the  poles  of  an  alternator  an  ordinary  carbon-filament  lamp 


FIG.    1. FILAMENT  POSITION  UNDER  FLUX  ACTION. 

carrying  a  direct  current  was  found  to  give  very  striking  and  definite 
results.  By  placing  the  lamp  in  the  region  of  the  leakage  flux  between 
adjacent  pole  tips  the  two  loops  of  the  filament  will  separate  widely  or 
draw  close  together,  depending  on  the  direction  of  the  flux.  By  progress- 
ing around  the  fields  with  a  lamp  in  this  manner  a  reversed  pole  or  a  dead 
pole  can  be  instantly  detected.  The  behavior  of  the  lamp  is  indicated  as 
shown  in  Fig.  1. 

Testing  Magnet   Coils   for   Short-circuits    (By  L.  J.   Todd).— The 
scheme  used  at  the  repair  shops  of  the  Cincinnati  Traction  Company  to 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


249 


test  motor-field  and  other  coils  for  short-circuited  turns  consists  in  link- 
ing the  open  coil  with  a  magnetized  iron  core,  as  shown  in  Fig.  1,  in 
this  way  forming  of  the  suspected  coil  a  transformer  secondary.  Local 
currents  will  then  flow  in  any  short-circuited  turns,  and  the  existence  of 
these  faults  will  be  indicated  by  the  increased  current  taken  by  the  core- 
magnetizing  windings,  as  well  as  by  the  development  of  heat  in  the  coils 
themselves. 

The  sketch  shows  the  construction  of  the  three-pole  laminated-steel 
core  used.     The  keeper  with  which  the  magnetic  circuit  is  completed  is 

Keeper 


FIG.    1. DIAGRAM  OF  CONNECTIONS. 


made  removable,  its  weight  alone  when  in  position  holding  it  in  ample 
contact  with  the  planed  surfaces  of  the  leg  laminations.  By  experiment 
the  exciting  energy  taken  by  the  core  alone  or  with  an  open-circuit  coil 
is  known  from  previous  determinations.  Then  if,  with  a  suspected  coil 
under  test,  the  wattmeter  indicates  an  amount  in  excess  of  this  value,  the 
faulty  coil  is  left  in  place  on  the  core  until  the  short-circuited  windings 
reveal  themselves  by  heating.  In  this  way  the  fault  can  be  accurately 
located  and  repaired. 

Commutator  Testing  Device  (By  F.  B.  Hays). — The  accompanying 
drawings  show  a  device  for  testing  magneto  commutators  installed  by  the 
Hercules  Electric  Company.  It  is  a  great  time-saver  as  compared  with 
other  methods  in  general  use  and  is  at  the  same  time  simple  to  operate  and 
absolutely  dependable.  At  the  Hercules  company's  works  a  boy  operat- 
ing the  device  tested  over  6000  commutators  in  one  ten-hour  day. 

A  plan  view  and  side  elevation  of  the  machine  are  shown  in  Fig.  1, 
in  which  A  is  the  bin  for  commutators  that  are  to  be  tested,  B  the  bin  for 
those  that  have  been  tested  and  have  been  found  all  right,  C  the  con- 
tact brushes  carrying  the  current  for  testing  each  commutator,  and  D 
the  bull's-eye  lamps  which  indicate  short-circuits  and  grounds  in  the 
commutators. 

The  method  of  testing  is  as  follows:     The  operator  places  a  commu- 


250 


HANDBOOK  OF  ELECTRICAL  METHODS 


tator  from  bin  A  horizontally  on  the  contact  brushes  C  in  such  a  manner 
that  each  end  of  each  segment  rests  on  a  brush  while  the  center  of  the 
commutator  rests  on  brush  No.  1.  Behind  each  brush  is  a  helical  spring 
which  presses  the  brush  upward,  thus  insuring  perfect  contact  between 


O 


000 

o0o   C 


O 


FIG.    1. COMMUTATOR  TESTING  DEVICE. 


the  brushes  and  the  commutator  segments.  If  a  short-circuit  exists 
between  two  of  the  segments,  the  two  bull's-eye  lamps  opposite  the  seg- 
ments will  show  a  dim  light.  If  the  commutator  is  grounded,  a  single 
bright  light  will  show. 


FIG.    2. DIAGRAM  SHOWING  CONNECTIONS  OF  COMMUTATOR  TESTING  DEVICE. 

Fig.  2  is  a  wiring  diagram  for  the  device.  A  short  study  of  this  dia- 
gram will  make  the  principle  upon  which  the  device  operates  perfectly 
clear.  It  will  be  noted  that  it  is  necessary  to  rotate  the  commutators 
through  an  arc  of  only  one  segment  to  test  all  segments  for  "a  ground." 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


251 


Testing  Armatures  with  Alternating  Current  (By  E.  W.  Copeland).— 
While  the  usual  method  of  testing  between  adjacent  commutator  bars 
with  a  millivolt  meter  will  indicate  short-circuited  or  poorly  soldered  leads 
by  a  low  reading  and  open-circuited  or  poorly  soldered  leads  by  a  high  one, 
it  often  occurs  that  an  armature  is  reinstalled  with  considerable  time  and 
labor  and  found  to  be  defective  after  all.  The  millivolt  or  drop  method 
merely  measures  the  resistance  of  each  coil,  but  when  an  armature  is 
subjected  to  magnetic  induction  an  e.m.f .  is  induced  in  its  winding  which 
will  cause  current  to  flow  in  the  turns  that  are  short-circuited.  Very  often 
one  turn  in  a  coil  is  forced  so  hard  against  another  that  the  insulation  is 
broken  and  the  turns  become  short-circuited.  In  such  a  case  the  milli- 
volt test  might  not  serve  to  detect  the  short-circuit,  and  as  a  consequence 


FIG.    1. METHOD  FOR  TESTING  ARMATURES. 

the  turns,  and  probably  the  coil,  would  be  destroyed  by  the  immense  cur- 
rent which  would  flow  in  the  short-circuited  turns  when  running  in  the 
magnetic  field  of  the  machine. 

A  simple  method  to  detect  such  defects  more  readily  requires  alternat- 
ing current,  whereby  an  alternating  flux  is  produced  by  a  U-shaped  magnet 
made  of  sheet  iron,  laminated  as  shown  in  Fig.  1.  When  an  alter- 
nating flux  flows  through  an  armature  coil  as  shown  an  e.m.f.  is  produced 
which  will  cause  current  to  flow  in  any  turns  that  are  short-circuited. 
This  current  will  set  up  a  strong  magnetic  flux  around  the  coil,  and  if  a 
piece  of  sheet  iron  is  held  near  it  will  vibrate  very  rapidly.  The  coil  will 
also  heat  very  rapidly,  and  if  the  magnet  is  large  enough  for  the  armature 
that  is  being  tested  the  coil  can  be  burned  out  completely.  This  method 
will  not  only  detect  coils  short-circuited  in  themselves,  but  will  detect 
one  coil  short-circuited  with  another,  as  well  as  reversed  coils.  Open- 
circuited  coils  can  be  located  by  touching  adjacent  commutator  bars 


252 


HANDBOOK  OF  ELECTRICAL  METHODS 


with  a  piece  of  wire.  If  the  coil  is  all  right  a  distinct  spark  will  be  noticed, 
but  if  it  is  open  there  will  be  none  at  all.  The  view  Fig.  1,  represents 
a  four-pole  armature  and  for  simplicity's  sake  only  one  coil.  When  all 
the  coils  are  in  place  if  the  armature  is  revolved  slowly,  holding  the  piece  of 
sheet  iron  over  the  side  of  the  armature  as  shown,  each  coil  will  be  in- 
fluenced and  tested  consecutively.  Of  course,  the  magnet  will  work 
equally  well  on  any  armature  within  its  range  of  sizes.  A  magnet — or, 
more  properly,  a  transformer — the  size  of  the  one  shown  to  be  used  on  104 
volts,  60  cycles,  will  serve  for  many  size  armatures.  It  is  wound  with 
sixty  turns  of  No.  6  magnet  wire.  When  using  this  magnet  it  should 
be  fastened  under  the  armature  and  the  armature  also  fastened  so  that 
the  core  of  the  armature  and  that  of  the  transformer  have  clearance 
enough  for  the  armature  to  be  revolved  without  touching  the  transformer 
core.  The  current  should  always  be  off  while  placing  the  transformer, 
as  well  as  when  it  is  not  in  use. 

Method  of  Locating  Grounds  in  Armatures. — It  is  often  very  difficult 
to  locate  a  low-resistance  or  "dead  ground"  in  a  low-voltage  armature 


Ground  to  Armature  Shaft 


FIG.    ]. LOCATING  GROUNDS  IN  ARMATURES. 

owing  to  the  very  low  resistance  of  the  windings  themselves.  In  such 
cases,  however,  the  following  method  can  be  employed  with  very  good 
success: 

First,  short-circuit  all  commutator  bars  by  winding  several  turns 
of  bare  copper  wire  around  them;  then  apply  a  source  of  energy,  direct 
current  preferred,  to  the  commutator  and  shaft.  The  voltage  to  be  used 
depends  upon  the  resistance  of  the  "ground." 

This  produces  a  circuit  from  the  commutator  through  the  grounded 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC.  253 

coil  to  the  ground  and  out  through  the  shaft,  thus  setting  up  a  field  around 
the  conductors  in  this  coil.  By  applying  a  small  piece  of  iron  to  the  sur- 
face of  the  armature  core  and  gradually  moving  it  around,  one  can  readily 
locate  the  grounded  coil  by  means  of  its  field,  which  attracts  the  iron. 

1  he  same  method  can  also  be  applied  to  alternating-current  apparatus, 
although  not  quite  so  readily.  For  example,  in  the  case  of  a  three-phase, 
single-circuit,  Y-connected  armature,  first  disconnect  the  Y,  splitting  the 
winding  up  into  three  separate  circuits.  Then  test  out  each  circuit  with 
a  magneto  or  some  similar  source  with  which  the  ground  can  be  located. 

Next  apply  a  current  to  one  end  of  the  grounded  circuit  and  to  the 
shaft.  Assume  that  there  are  twelve  coils  in  this  circuit,  coil  No.  7  being 
the  grounded  coil,  while  coil  No.  1  is  connected  to  the  line  as  shown  in  the 
accompanying  sketch,  page  252. 

There  will  then  be  a  circuit  through  coils  Nos.  1,  2,  3,  4,  5,  6  and  7 
which  can  be  readily  detected  with  a  piece  of  iron  as  previously  explained, 
while  coils  Nos.  8,  9,  10,  11  and  12  are  dead. 

It  is  then,  of  course,  obvious  that  if  coils  1,  2,  3,  4,  5,  6  and  7  carry  a 
current  while  coils  8,  9,  10,  11  and  12  carry  no  current,  the  ground  must 
be  in  some  section  of  coil  No.  7,  the  circuit  being  completed  at  this  point. 

Remedying  Trouble  Caused  by  Varying  Voltage. — Motors  are  often 
operated  from  street  railway  circuits  on  which  there  is  a  wide  variation 
in  voltage  during  the  day.  In  one  case  a  compound  motor,  rated  normally 
at  550  volts,  was  used  to  drive  a  centrifugal  pump  taking  water  from  a 
deep  well  to  augment  the  water  supply  of  a  city.  There  was  a  variation 
of  about  100  volts  from  the  highest  to  the  lowest  voltage  during  the  day 
at  the  panel  controlling  the  motor.  This  caused  the  motor  to  run  above 
normal  speed  on  the  higher  voltage,  and  as  the  load  on  the  pump  corre- 
sponding to  this  speed  was  too  large  for  the  motor  to  carry,  trouble  was 
constantly  experienced  from  the  opening  of  the  circuit-breakers.  The 
load  on  a  centrifugal  pump  under  constant  head  is  of  such  a  character 
that  a  slight  increase  in  the  speed  of  the  pump  causes  a  large  increase  in 
the  load  on  the  motor.  After  making  tests  it  was  decided  to  increase 
the  number  of  turns  in  the  series  field  coils  so  that  when  the  motor  was 
running  at  normal  voltage,  and  consequently  at  normal  speed,  more  of 
the  excitation  would  be  supplied  by  the  series  field  coils  than  formerly, 
and  by  placing  a  rheostat  in  the  shunt  field  circuit,  the  excitation  from  the 
shunt  coils  was  decreased,  the  total  excitation  remaining  the  same  as 
before  at  normal  voltage.  When  the  higher  voltage  occurs  the  increased 
current  has  a  greater  effect  on  the  field  than  before,  owing  to  the  greatest 
number  of  series  turns,  and  the  speed  is  not  increased  enough  to  change 
the  load  materially. 

Conversion  of  550-volt  Generator  to  Edison  Three-wire  Service 
(By  J.  H.  Bradbury,  Jr.). — The  generating  station  of  the  Topeka  (Kan.) 


254 


HANDBOOK  OF  ELECTRICAL  METHODS 


Edison  Company  produces  550-volt  direct  current  for  the  local  railway 
as  well  as  110— 220- volt  Edison  three-wire  service  for  its  own  customers. 
The  accompanying  Fig.  1  shows  how  J.  I.  Chase,  engineer  in  charge, 
has  arranged  switches  in  the  circuits  of  one  of  his  500-kw.,  550-volt 
engine-driven  railway  generators,  making  this  machine  available  for 
220-volt  operation.  The  series  compensating  coil  is  first  short-circuited 
by  closing  a  switch  in  the  base  of  the  machine,  while  opening  another 
switch,  on  the  generator  panel,  introduces  a  prearranged,  fixed  resistance 
into  the  field  circuit,  reducing  the  excitation  to  the  value  where  220  volts 
will  be  developed.  Closer  adjustment  is  made  with  the  field  rheostat  as 

Fixed  Resistance 


FIG.    1.- 


250V. 
CONVERTING  550-VOLT  GENERATOR  TO  220-VOLT  SERVICE. 


before.  At  the  rear  of  the  board  are  disconnect  switches  for  throwing  the 
machine  leads  from  the  500-volt  to  the  220-volt  bases.  At  550  volts  the 
generator  is  rated  to  deliver  only  830  amp.,  but  no  difficulty  is  found  in 
taking  currents  as  large  as  1000  amp.  at  220  volts,  and  the  operation  of 
the  unit  has  proved  most  satisfactory  under  the  converted  conditions 
besides  adding  nearly  250  kw.  to  the  220-volt  capacity  of  the  station. 

no-volt  Shunt  Motor  on  a  22o-volt,  Three-wire  Circuit  (By  John 
Burns). — A  friend  of  mine  recently  asked  my  advice  about  the  cost  of 
having  his  2-h.p.,  110-volt  shunt  motor  rewound  for  220  volts,  as  the 
central-station  company  refused  to  allow  him  to  continue  operating  his  ma- 
chine across  only  one  side  of  its  Edison  three- wire  system,  claiming  that  its 
operation  tended  to  unbalance  the  lines.  The  cost  of  reconstruction  as 
estimated  by  a  local  electrical  company  really  exceeded  the  second-hand 
value  of  the  motor,  which  was  an  old  one;  and  as  the  service  it  rendered 
was  only  occasional  and  at  slow  speeds,  such  a  change  did  not  seem  worth 
while.  After  examining  the  case,  it  occurred  to  me  that  at  the  low  speeds 
commonly  employed  (control  being  secured  by  manipulating  the  starting 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


255 


rheostat  in  the  armature  circuit)  the  current  taken  by  the  armature 
probably  would  not  much  exceed  that  taken  by  the  field,  and  the  two 
might  accordingly  be  connected  in  series  across  the  110— 220-volt,  three- 
wire  system  with  the  neutral  tapped  in  without  much  unbalancing.  I 
tried  this,  first  taking  the  precaution  of  reversing  the  armature  brush 
leads  to  secure  the  same  direction  of  motor  rotation.  The  motor  started 
up  as  usual,  and  at  none  of  the  loads  it  was  called  upon  to  pull  did  the 
armature  circuit  take  current  exceeding  that  of  the  field  winding  by  more 


FIG.    1. DIAGRAM  OF  MOTOR  CONNECTIONS. 


than  the  demand  of  a  32-c.p.  carbon-filament  lamp.  When  this  fact  was 
shown  to  the  company's  inspector,  he,  of  course,  was  satisfied,  as  the 
unbalancing  now  produced  by  the  motor  did  not  exceed  the  effect  of 
turning  on  a  single  lamp.  This  110-volt  motor  accordingly  is  now  run- 
ning with  its  armature  and  field  virtually  in  series  across  220  volts,  the 
neutral  being  connected  in  to  carry  the  difference  in  demand  of  the  two 
windings,  and  the  expense  of  rebuilding  it  has  been  avoided  by  a  few 
simple  changes  in  connections.  The  arrangment  is  shown  in  Fig.  1. 

A  Method  of  Raising  Inverted  Motors  (By  H.  T.  Boynton)  .—There 
are  many  methods  of  raising  an  inverted  motor  to  a  location  on  a  ceiling. 


250 


HANDBOOK  OF  ELECTRICAL  METHODS 


The  one  outlined  herein  will  be  found  excellent  under  certain  conditions. 
Fig.  1  shows  how  the  tackle  is  arranged  and  Fig.  2  illustrates  a  plan  view 
at  the  second  floor.  In  the  method  described  here  the  inverted  motor 
is  raised  with  two  ropes.  Each  passes  through  a  foundation-bolt  hole  in 
the  bed-plate,  is  arranged  around  the  motor  frame  and  is  made  fast  in 

Cast  Iron  Washer^     Floor  of  Third  Story    A     /Temporary  Plank 
.J -I         . ..  /  \^T  — I 


Temporary  Eye  Bolt 


Heavy  Horse 


Bed  Plate  ^M 


• 

• 

^Floor 
Beam 

***  Holes  through  Floor  ^ 

\5>-  i  ,-." 

\xR 

1 

i 
i 

i 

^ 

Stringer  ' 
for  Motor 

Stringei 
Bolt 

y 

FIG.    1. SIDE  ELEVATION  OF  HOISTING  OUTFIT. 

the  eye-bolt  at  what  is  normally  the  top  of  the  motor.  The  two  holes 
in  the  bed-plate  through  which  the  hoisting  ropes  pass  are  located  at 
diagonally  opposite  corners.  The  hoisting  ropes,  after  being  made  fast 
to  the  motor,  are  threaded  through  two  of  the  four  holes  which  have  been 
bored  to  accommodate  the  bolts  in  the  stringer  pieces  which  will  support 
the  motor.  Then  the  ropes  are  carried  through  two  accurately  located 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


257 


holes  in  the  floor  above.  On  this  floor  rests  a  horse  which  supports  the 
two  sets  of  blocks  with  which  the  motor  is  raised.  As  indicated  in  Fig. 
2,  the  horse  is  arranged  diagonally  so  that  it  is  directly  over  the  two  holes 
in  the  floor  through  which  the  hoisting  ropes  pass.  Sometimes  instead  of 


Floor  of  Second  Story 


Stringer 
Bolts 


£  a 


Hole  in  Stringer 
and  in  Bed  Plate 


Center  Line 
of  Horse 


Hoisting  Rope 
Passes  through 
these  two  Holes 

" 


v- 


•y— 


x         Outline  of  Motor  Frame 
FIG.    2. PLAN  VIEW  ON  SECOND  FLOOR. 


ten 


using  a  horse  to  support  the  tackle,  it  is  best  to  arrange  temporary  eye- 
bolts  in  the  floor  of  the  story  next  above  as  shown  at  A  and  A.  They  can 
be  readily  removed  when  the  motor  has  been  raised,  but  can  be  quickly 
replaced  when  the  motor  must  be  replaced  or  taken  down.  After  a  motor 

Floor  of  Second  Story  \^ 


£ 


Stringer 


\  Hole  for  Motor 
Supporting  Bolt 


Stringer  Bolt 
FIG.    3. METHOD  OF  LOCATING  BOLT  HOLES. 

has  been  raised  to  its  position  on  the  stringer  planks  two  bolts  are  inserted 
through  the  open  holes  and  set  up  tightly.  Then  the  hoisting  ropes  are 
pulled  out  and  the  other  two  bolts  are  inserted.  It  should  be  noted  that 
with  this  method  it  is  not  necessary  to  cut  any  large  holes  in  floors. 


258 


HANDBOOK  OF  ELECTRICAL  METHODS 


The  stringer  pieces  having  been  bolted  to  the  beams,  the  four  holes,  two  in 
each  stringer,  for  the  four  motor-supporting  bolts  are  located  and  bored 
in  them.  These  holes  should  be  at  least  1/8  in.  greater  in  diameter  than 
the  diameter  of  the  supporting  bolts.  Then  the  two  holes  for  the  ropes 
are  bored  through  the  floor  above.  If  a  bit  long  enough  is  available  this 
is  easily  done  by  using  the  holes  in  the  stringers  as  guides  and  boring  with 
the  lower  end  of  the  bit  through  one  of  them.  If  no  long  bit  is  at  hand  the 
locations  of  the  floor  holes  can  be  accurately  determined  with  a  plumb- 
bob,  as  shown  in  Fig.  3.  The  floor  holes  should  be  generously  large  so 
that  they  will  not  bind  the  hoisting  rope.  When  buying  a  motor  for 
inverted  ceiling  mounting  or  for  mounting  in  any  position,  one  should 
be  selected  which  has  a  single  bed-plate  instead  of  two  slide-rails.  It  is 
much  more  difficult  and  tedious,  therefore  expensive,  to  line  up  and  level 
two  slide-rails  than  one  bed-plate.  Furthermore,  the  slide-rails  will 
require  at  least  twice  as  many  supporting  bolts  as  will  the  bed-plate. 

A  Safety  Panel  for  Cranes  (By  F.  L.  Thome). — In  an  endeavor  to 
prevent  the  accidents  which  continually  occur  through  careless  handling 
of  cranes  in  a  large  mill  the  following  control  panel  has  been  designed  to 


E       E        E 
FIG.    1. DIAGRAM  OF  CONNECTIONS   FOR   SAFETY    PANEL. 

replace  the  usual  panel  furnished  in  the  cage  of  a  bridge  crane.  It  is 
intended  to  prevent  such  accidents  as  are  caused  by  the  operation  of  the 
cranes  by  unauthorized  persons,  by  the  unintentional  or  accidental  manipu- 
lation of  a  controller  while  some  person  is  working  on  or  about  the  crane 
under  the  impression  that  it  will  not  be  operated,  by  a  "dead"  supply 
becoming  "alive"  while  a  controller  may  be  in  an  "on"  position  with  no 
one  in  the  cage,  and  by  various  other  unexpected  conditions.  It  has 
become  absolutely  necessary  not  to  rely  on  the  operator  or  others  whose 
duties  require  them  to  be  about  the  cranes  if  it  can  be  avoided.  Fig.  1 
is  a  diagram  of  the  connections  of  the  panel  and  Fig.  2  a  front  view  of  the 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


259 


panel  as  mounted  in  its  box  in  the  crane  cage.  The  main  service  switch 
is  provided  principally  to  satisfy  the  insurance  requirements,  and  as  it  is 
present  it  has  been  considered  advisable  to  provide  the  opening  in  the 
panel-box  door,  through  which  it  may  be  operated,  as  an  additional  means 
of  opening  the  main  circuit  in  case  of  emergency.  All  ordinary  main- 
line control  is  by  the  push  buttons  C  and  D  operating  the  magnetic  switch 
F,  C  being  used  to  close  and  D  to  open  the  switch,  as  indicated  in  the  dia- 
gram. It  will  be  seen  that  the  operating  coil  of  this  switch  is  so  connected 
that  when  the  switch  is  open  the  coil  circuit  is  open.  As  the  switch  is 
held  closed  by  the  energized  coil,  any  break  in  the  coil  circuit  or  failure  of 


"© 


QE  QEQE 


FIG.    2. FRONT  VIEW  OF  PANEL. 

voltage  therein  will  allow  the  switch  to  open.  As  long  as  there  is  no  vol- 
tage in  the  main  circuit  the  switch  will  remain  inoperative,  but  if  the  main 
circuit  is  alive  the  switch  may  be  closed  by  pushing  button  C,  which  shunts 
the  break  due  to  the  switch  being  open.  Button  D  being  pushed  opens 
the  coil  circuit  and  allows  the  switch  to  open.  If  any  of  the  safety  plugs 
E  be  removed  the  switch  must  remain  open  until  they  are  returned,  as 
their  absence  opens  the  circuit  and  the  switch  cannot  be  operated.  The 
object  of  the  plugs  E  is  that  anyone  having  one  of  these  plugs  in  his  pos- 
session may  be  assured  that  the  crane  is  inoperative  until  he  replaces  it. 
The  lamp  A  indicates  by  its  incandescence  that  the  trolleys  are  alive,  and 
the  lamp  B  indicates  in  like  manner  that  the  panel  is  alive  on  the  load  side 
of  the  magnetic  switch.  Fig.  2  illustrates  the  appearance  of  the  com- 
pleted panel  box  as  mounted  in  the  crane  cage.  The  box  is  of  sheet 
steel  following  standard  panel-box  construction  with  the  exception  of 
depth,  which  is  made  great  enough  to  accommodate  the  magnetic  switch. 
The  door  is  locked  and  control  of  this  magnetic  switch  is  had  by  the  push 
buttons  before  mentioned,  which  are  mounted  at  one  side  of  the  door. 


260 


HANDBOOK  OF  ELECTRICAL  METHODS 


The  window  in  the  door  is  designed  to  allow  the  indicating  lamps  to  be 
seen  and  the  handle  of  the  service  switch  to  be  reached.  Other  parts  of 
the  panel  are  inaccessible  to  any  one  but  the  electrician  who  carries  the 
key.  The  three  plugs  E  have  a  round-knob  head  painted  bright  red  and 
on  the  door  above,  with  an  arrow  pointing  to  them,  is  a  notice  directing 
any  person  working  on  the  crane  to  remove  and  keep  in  his  possession  one 
of  these  plugs  until  his  work  is  completed  and  he  is  leaving  the  crane,  and 
all  employees  whose  work  brings  them  on  or  about  the  cranes  are  person- 
ally instructed  to  the  same  effect.  Three  plugs  are  considered  sufficient, 
but,  of  course,  more  can  be  added  if  thought  necessary.  Suppose  that  an 
electrician  and  a  machinist  are  sent  to  work  on  a  crane,  the  crane  runway 
or  some  other  apparatus  where  the  crane  might  interfere  with  them.  One 
arrives  and  removes  a  plug,  puts  it  in  his  pocket  and  goes  to  work.  Soon 
the  other  arrives  and  in  turn  takes  possession  of  another  plug.  At  the 
completion  of  his  work  each  one  replaces  his  plug.  From  the  time  the 
first  plug  is  removed  until  the  last  is  replaced  the  crane  cannot  be  oper- 
ated. In  this  way  it  is  hoped  in  the  future  to  avoid  accidents  due  to 
carelessness  and  definitely  to  place  the  responsibility  for  any  such  as 
may  occur. 

Methods  of  Mounting  Motors  on  Side  Walls  and  Columns  (By  H.  F. 
Bearnes). — In   wooden  buildings  motors   of  moderate   output   can  be 


Roof  Truss 


Line  Shaft 


\Yellow  Pine  Cleat 


Bolt 


FIG.    1. MOTOR  MOUNTED  ON  CLEATS  AT  SIDE  WALL. 

mounted  on  the  side  walls  as  shown  in  Fig.  1.  Substantial  cleats,  prefer- 
ably of  yellow  pine,  are  bolted  to  wall  posts  and  the  bed-plate  of  the 
motor  is  bolted  to  these.  Lag  screws  should  not  be  used  (unless  many 
can  be  driven  in)  because,  although  they  may  appear  to  be  quite  firm 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


261 


when  inserted,  the  vibration  of  the  motor  tends  to  loosen  them  and  they 
may  pull  out.  Bolts  securing  the  cleats  will  extend  entirely  through  the 
posts  and  to  the  outside  of  the  building.  Depressions  should  be  arranged 
in  the  outside  surface  of  the  wall,  as  indicated  in  Fig.  1,  into  which  the 
bolt  heads  can  be  set.  Pieces  of  board  should  be  nailed  over  the  depres- 
sions so  that  water  from  rain  or  snow  cannot  drip  from  the  bolt  heads  and 
make  streaks  on  the  wall.  In  wooden  buildings,  small  motors  can  usually 
be  bolted  directly  to  the  posts  or  columns.  In  buildings  of  weak  construc- 
tion it  is  sometimes  necessary  to  build  wooden  frames,  extending  from 
floor  to  ceiling  and  strongly  braced,  to  carry  motors  located  on  side  walls. 
Although  such  frames  often  rest  directly  against  a  wall  they  are  structur- 
ally independent. 


FIG.    2. WOODEN  WALL  BRACKETS  FOR  MOTORS. 

Where  motors  must  be  located  at  side  walls,  it  appears  to  be  the  pres- 
ent tendency  to  mount  them  directly  on  the  walls,  as  outlined  in  Fig.  1 
rather  than  on  brackets.  When  a  motor  is  arranged  with  its  bed-plate 
in  a  vertical  plane  the  erector  should  always  be  certain  that  the  motor 
end  frames  are  so  located  in  relation  to  the  main  frame,  that  the  oiling 
devices  will  feed  properly.  It  is  the  usual  practice  of  electrical  machine 
manufacturers  to  ship  motors  with  their  bed-plates  arranged  for  operation 


262 


HANDBOOK  OF  ELECTRICAL  METHODS 


in  a  horizontal  plane  and  below  the  motor  frame  —  that  is  to  say,  the 
motors  are  ordinarily  shipped  for  floor  mounting.  A  motor  arranged 
for  floor  mounting  can,  as  a  rule,  be  adapted  for  wall  mounting  by  remov- 
ing the  end  frames  (which  carry  the  bearings),  rotating  them  through  an 
angle  of  90  deg.  and  replacing  them. 

Some  erectors  prefer  to  mount  motors  located  at  side  walls  on  brackets. 
A  wooden  motor-bracket,  designed  for  mounting  on  a  brick  side  wall,  is 


Plank  Flooring 


Punched 

Hole  for 

Supporting 

Bolt 


Front  Elevation  Side  Elevation 

PIG.    3. STRUCTURAL  STEEL  BRACKET  SUPPORTS. 

illustrated  in  Fig.  2.  Brackets  of  this  design  were  used  for  supporting 
15-h.p.  and  20-h.p.  motors  in  the  Omaha  (Neb.)  shops  of  the  Union 
Pacific  Railroad  Company.  The  bolts  supporting  the  brackets  extended 
entirely  through  the  brick  walls  and  each  had  a  substantial  washer  under 
its  head. 

Where  many  brackets  are  to  be  used  it  is  usually  economical  to  have 
a  pattern  made  and  to  use  bracket  supports  of  cast  iron  rather  than  of 


l/WVl/A 

Side  Elevation  Front  Elevation 

FIG.    4. WOODEN  COLUMN  BRACKET. 

wood.  The  pattern  for  this  is  easily  made  in  one  piece.  Holes  to  accom- 
modate the  bolts  for  binding  the  supports  to  a  wall  and  for  clamping  the 
bottoms,  to  which  the  floor  boards  are  nailed,  are  drilled  in  the  casting 
by  the  erector.  Wall-bracket  supports  can  be  made  of  structural  steel 
angles  and  steel  plates,  as  suggested  in  Fig.  3.  Obviously,  steel  supports 
are  preferable  to  cast-iron  ones,  as  for  equal  strength  they  are  lighter  and 
they  are  not  so  brittle.  Another  point  in  favor  of  steel  construction  is 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


263 


that  when  it  is  taxed  beyond  its  capacity  it  will  give  an  indication  of 
distress  before  failing,  whereas  cast  iron  may  crack  without  warning. 
Where  facilities  are  available  for  shearing  plates  and  structural  sections 
and  for  riveting  them  together  economically  steel  bracket  supports  have 
much  to  commend  them. 

Motors  are  often  advantageously  mounted  on  columns.  Fig.  4  shows 
the  construction  of  a  simple  form  of  column  bracket.  This  construction 
can  be  used  only  where  motors  of  relatively  small  output  are  involved. 
The  braces  and  beams  are  clamped  to  the  column  with  lag  screws,  each 
having  a  punched  washer  under  its  head.  Enough  lag  screws  should  be 
used  so  that  there  can  be  no  possibility  of  their  working  loose.  The  upper 


...A-  -A 


Mounting 
Board  - 


Concrete 
Column 


IH' 


Wrought 
Iron"U" 

Bolt 
34"Rod 

2"x  4" 
Batten 


U^. 
cj      4.  •  Punched 

Section     Washer 
A-A 


Floor 


Front  Elevated 

FIG.    5. MOUNTING  BOARD  FOR  REINFORCED  CONCRETE  COLUMN. 

end  of  each  brace  is  set  about  1/2  in.  into  the  beam  and  is  held  there  with 
wood  screws.  It  is  well,  as  a  rule,  to  use  matched  stock  for  motor 
brackets.  If  plain  stock  is  used  it  ultimately  dries  out  and  shrinks,  leav- 
ing open  spaces  between  adjacent  boards  for  dust,  dirt  and  probably  oil 
to  come  down  continually  through  the  spaces.  This  is  largely  avoided 
where  bracket  floors  are  made  of  " matched"  stock.  They  can  then  be 
cleaned  systematically  by  the  motor  inspector. 

In  buildings  of  reinforced  concrete  small  motors  can  be  mounted  on  a 
mounting  board  like  that  of  Fig.  5.  It  is  sometimes  advisable  when 
erecting  this  kind  of  mounting  board  to  chip  out  a  groove  for  each  of  the 
"U-bolts"  in  the  rear  face  of  the  column.  By  this  expedient  any  tend- 
ency for  the  mounting  to  slip  down  the  column  is  corrected.  The  wood 
used  should  be  well  seasoned  so  that  there  will  be  but  little  shrinkage. 
Starting  devices  for  motors  can  also  be  mounted  on  boards  like  that  of 
Fig.  5.  Obviously,  lighter  construction  may  be  used  for  these. 

A  neat  and  economical  bracket  for  a  structural  steel  column  is  illus- 

18 


264 


HANDBOOK  OF  ELECTRICAL  METHODS 


trated  in  Fig.  6.  A  steel  plate  forms  the  floor  or  platform  and  all  of  the 
components  of  the  bracket  are  riveted  together.  Bolts  are  used  to  attach 
the  bracket.  A  portable,  electrically  operated  breast  drill  and  an  "old 
man"  to  maintain  it  in  operating  position  will  be  found  valuable  tools 


"~o  —  o~ 

-3—0- 

_-=.—=.•=; 
-<  

A_. 


Square 

Headed 

Bolts 


Steel 
-  Plate 
Platform 

Counter-Sunk 
Head  Rivet 


'V* 

o  \yr 


Steel 
Plate 
Brace 


Steel 
Angle 


FIG.    6. STRUCTURAL  STEEL  MOTOR  BRACKET  AND  COLUMN. 

Wall  of  Building 


Line  Shaft  A 


Pulley 
i  i  Belt 


Column 


Motor  Platform     ;     /  Motor  A 

^A  Column 


Motor  B 


Line  Shaft  B 


Wall  of  Building 
FIG.    7. MOTOR  PLATFORM  BETWEEN  COLUMNS. 

where  much  drilling  is  to  be  done  in  structural  steel  members  already 
erected.  The  outfit  will  pay  for  itself  in  a  short  time.  Where  a  bracket 
must  be  attached  to  the  face  of  a  column  instead  of  to  its  side  it  can  be 
arranged  like  the  one  shown  in  Fig.  3.  Countersunk-head  rivets  should 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


265 


be  used  to  secure  the  platform  plate.     Button-head  rivets  interfere  with 
the  locating  of  a  motor  bed-plate  on  a  platform. 

In  arranging  group  drives  it  frequently  occurs  that  two  motors  can 
be  advantageously  mounted  on  one  platform,  supported  by  two  columns, 


~^: 

Position 

—  ^ 

Motoij 

N-^-. 

/ 

\of  Motor 

Motor  A 

~1 

B 

1 

o 

j   Pulley 

|- 

~~*\ 

... 

/       JO 

\           \ 

i 

?"~"~"\ 

•  —  ~~          " 

i           |__.| 

i 

I    O   / 

Position 

I      rt  J 

^~"' 

of  Motor 

Pulley  ^4. 

'          '  ' 

—  ^-  O 

_,           i. 

f  L-^—  ---^-v 

r~ 

tr: 

0          0 

;         Matched  / 

-^ 

v\ 

— 

7/*" 

Flooring 

1 

' 

N. 

\/0 

/ 

End  Bracket 

Lag  Screws 

| 

c 

4 
^ 

and    X 
Washers 

\i/ 

Brace 

Wooden 

Column 

Floor  Line 

Section  C  C  Side  Elevation 

FIG.    8. WOODEN  PLATFORM  FOR  TWO  MOTORS. 


Plan  View 

Steel  l-Beam 
Stringers 


Clamping  Bar 


Cast  _ 

Iron  "^ 

Bracket 


Structural 
—  Steel 
Column 


FIG.    9. STRUCTURAL  STEEL  STRINGERS  AND  SUPPORTS. 

as  indicated  in  the  plan,  Fig.  7.  The  starting  device  for  each  motor  can 
be  mounted  on  the  adjacent  column  near  the  floor.  In  a  wooden  building, 
a  platform  of  this  type  can  be  constructed  as  suggested  in  Fig.  8.  The 
motors  are,  if  possible,  located  close  to  the  columns  so  that  the  bridge 


266 


HANDBOOK  OF  ELECTRICAL  METHODS 


between  the  brackets  can  be  made  of  the  lightest  material  possible  and 
yet  be  stiff  enough  to  carry  the  motors. 

Stringers  made  of  structural  steel  I-beams  or  channels  serve  to  sup- 
port the  motors  in  steel-frame  buildings  where  two  motors  can  be  arranged 
to  drive  from  between  adj acent  columns.  A  typical  installation  is  outlined 
in  Fig.  9.  Only  one  motor  is  shown  on  the  stringers  in  the  illustration, 


Drill  Holes 
to  Suit  Holes 
in  Stringer 


Plan  View 


This  surface 

Bolts  against 

Face  of 

Column 


Front  Elevation         Side  Elevation 
FIG.    10. DETAIL  OF  CAST-IRON  END  BRACKET. 


but  another  or  more  could  be  supported.  The  feature  of  this  method  of 
mounting  is  the  cast-iron  end  bracket  (see  Fig.  10  for  detail),  which  carries 
the  stringers  at  the  columns.  End  brackets  can  be  made  from  structural 
steel,  but  it  is  not  always  possible  to  make  them  so  they  can  compete  in 
cost  with  cast-iron  ones.  It  is  usually  possible  to  design  one  cast-iron 
end  bracket  that  it  can  be  used  for  a  majority  of  applications  about  a  plant. 


Steel  Channel/ 


Strap  Iron 
Lattice  Bars 

Plan  View 


End 
Elevation 


FIG.    11. LATTICED  CHANNEL  STRINGERS. 

Different  drillings  will  be  necessary  to  adapt  the  brackets  for  different 
columns  and  stringers,  but  the  same  pattern  and  castings  can  be  used  for 
all.  In  designing  such  an  end  bracket  it  should  be  made  sufficiently 
strong  to  carry  the  largest  motors  that  it  will  ever  be  called  upon  to  bear. 
This  procedure  will  render  it  too  heavy  for  supporting  small  motors,  but, 
unless  there  are  many  small  motors,  it  will  be  more  convenient  and  prob- 
ably more  economical  to  make  all  end-bracket  castings  from  the  same 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


267 


pattern.     It  should  be  noted  that  the  pattern  is  of  one-piece  construction 
and  is  easily  and  cheaply  made. 

No  floor  is  necessary  with  the  construction  shown  in  Fig.  9.  The 
motor  bed-plate  is  clamped  to  the  stringers,  possibly  by  one  of  the 
methods  suggested  in  Figs.  13  and  14.  These  will  be  discussed  later. 


t  - 


------  =.--=-«=  =  -====-=.-=^^:===  =  -  --=.-=£31:  -  J 

-if       7       I  I 


f=    -c-3^                                 cT           -f-                   -t'f- 

E^j/ 

kr-oJ 

Structural  Steel  I-Beams 
Plan  View 

IronPipey     End 
Spacers     Elevation 

1 

1 

« 

End 

H                           a                             Q 

E3 

1 

I/ 

Structural  Steel  Channels 

Punched 
Washers 

Plan  View 
FIG.    12. ASSEMBLED  STRINGERS. 


Elevation 


Bed  Plate-r— — i 

""  Clamping    1 1  If       Detail  of  Angle  Bar 


Channel 

Iron — - 
Stringer 


Cli 

t 


Bolt 


FIG.    13. APPLICATION  OF  ANGLE-CLAMPING  BAR. 


Steel  Channel 
Stringer 


FIG.    14. CHANNEL-CLAMPING  BARS. 


The  stringers  may  be  single  channels  (Fig.  11)  or  single  I-beams,  or  they 
may  be  assembled  from  two  or  more  channels  or  I-beams,  bolted  together, 
as  detailed  in  Fig.  12.  If  stringers  are  long  and  lateral  deflection  is  feared 
the  members  may  be  reinforced  with  lattice-bars,  as  shown  in  Fig.  11. 
In  the  assembled  stringers  of  Fig.  12  short  lengths  of  pipe  are  used  as 


268 


HANDBOOK  OF  ELECTRICAL  METHODS 


spacers  in  the  member  A,  which  is  composed  of  I-beams,  and  punched 
washers  are  used  for  B,  which  is  made  up  of  channels.  If  many  assembled 
stringers  are  to  be  used  it  may  be  cheaper  to  have  regular  spacers  made  of 
cast  iron  than  to  use  the  pipes  and  washers. 

One  of  the  simplest  methods  of  clamping  a  motor  to  steel  stringers  is 
outlined  in  Fig.   13.     A  length  of  angle  iron,  properly  drilled,  is  used 

Core  Hole 
§' larger  than  Bolt 


Make  to  Fit 
Flange  of_\ 
I-Beam 


FIG.    15. — BEAM  WASHERS  AND  FLANGE  WASHER. 

for  a  clamping  bar  and  standard  bolts  passing  through  the  motor  bed-plate 
hold  the  components  in  correct  relation.  The  method  shown  in  Fig.  14 
is  sometimes  used  where  large  motors  are  involved.  In  this  case  small 
channels,  possibly  3  in.  or  4  in.  deep,  are  used  for  clamping  bars.  A  clamp- 
ing piece  (see  detail  in  Fig.  14)  forged  from  a  wrought-iron  bar  is  used  to 
prevent  the  clamping  bars  from  spreading.  If  enough  will  be  used  to 

Open  Holes  for  Motor - 
/  holding  Bolts 


df                  ~\> 

I 

Flat  Head     / 

/ 

Bolts     / 

Steel 

Plate 

1 

|o|       |o|       |o| 

o                        o 

Plan  View 


Flange  Washers 


Steel  Channel 

Side  Elevation 

FIG.    16. STEEL  PLATE  PLATFORM. 

make  it  worth  while  to  have  them  cast  I-beam  washers  of  iron,  similar  to 
that  of  Fig.  15,  A,  should  be  used  instead  of  the  forged-iron  clamping 
piece  shown  in  Fig.  14. 

Sometimes  it  is  convenient  to  bolt  a  steel  plate  for  supporting  a  motor 
to  stringers,  as  shown  in  Fig.  16.  The  plate  is  drilled  for  the  bolts  that 
hold  down  the  motor  bed-plate.  Flathead  bolts  should  be  used  for  at- 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC.  269 

taching  the  platform  plate  to  the  stringers  so  that  there  will  be  nothing 
extending  from  its  surface  to  interfere  with  the  lateral  adjustment  of  the 
motor.  Flange  washers  (Fig.  15,  B)  which  are  beveled  to  fit  the  insides  of 
flanges  of  I-beams  and  channels,  are  used  under  the  nuts  of  flat-head  bolts. 

Insulating  and  Grounding  Motors  and  Generators  (By  Terrell  Croft) . 
—The  National  Electrical  Code  specifies  that  motors  and  generators 
operating  at  pressures  in  excess  of  550  volts  must  have  their  base  frames 
permanently  and  effectively  grounded.  Motors  and  generators  operating 
at  pressures  of  550  volts  or  less  should,  so  the  code  specifies,  be  insulated 
from  the  ground  wherever  feasible,  but  where  the  insulation  of  the  frame 
is  impracticable  permission  may  be  secured  from  the  local  inspection 
department  to  omit  the  frame  insulation.  However,  where  such  insula- 
tion is  omitted  the  frame  must  be  thoroughly  grounded. 

Insulating  the  frame  of  a  high-voltage  machine  from  the  ground  in- 
troduces a  dangerous  life  hazard,  because  there  may  be  a  leak  between  the 
winding  and  the  frame  and  the  attendant  touching  such  a  frame  can  be 
severely  shocked,  or  possibly  killed.  Where  the  voltage  is  low — below 
possibly  550 — this  element  of  life  hazard  is  not  of  great  moment.  It  is 
therefore  evident  that  the  frames  of  all  high-voltage  machines  should  be 
thoroughly  grounded,  and  it  is  also  very  likely  true  that  it  would  be  well 
to  ground  the  frames  of  all  low- voltage  machines  to  protect  the  attendants 
from  shock. 

There  is  another  good  reason  why  it  is  preferable  from  the  operator's 
standpoint  to  ground  the  frames  of  all  electrical  machinery.  Consider 
the  case  of  a  frame  of  a  machine  insulated  from  the  ground:  If  a  leak 
occurred  in  this  machine  between  one  of  the  windings  and  the  frame, 
the  operator  would  not,  in  the  ordinary  course  of  operation,  be  advised 
of  its  presence,  and  another  ground  might  occur  in  the  same  machine 
between  the  winding  and  the  frame,  which  would  make  a  short-circuit 
and  possibly  burn  out  the  machine  and  produce  a  fire.  If,  however,  the 
frame  of  the  machine  were  thoroughly  grounded,  a  leak  between  the 
frame  and  the  winding  would  make  itself  known  through  an  indication 
on  the  station  ground  detector,  and  then  it  could  be  readily  corrected 
before  another  ground  could  occur  and  make  serious  trouble. 

The  intention  of  the  code  rule  appears  to  be  that  if  a  frame  is  insulated 
it  must  be  thoroughly  insulated,  and  if  grounded,  thoroughly  grounded. 
If  a  frame  were,  however,  but  imperfectly  insulated,  sufficient  current 
might,  under  certain  conditions,  flow  through  the  high-resistance  path 
constituted  by  the  imperfect  insulation  and  cause  a  fire.  Although  the 
code  does  not  so  specify,  it  is  probable  that  it  is  always  best  to  ground 
effectively  electrical  machinery  frames  wherever  possible,  but  where 
effective  grounding  is  not  feasible  the  frame  should  be  thoroughly  insulated 
for  the  reason  just  indicated. 


270 


HANDBOOK  OF  ELECTRICAL  METHODS 


It  does  not  appear  to  be  general  practice  among  Underwriters'  in- 
spectors rigidly  to  enforce  the  code  requirement  for  thorough  insulation. 
Some  inspectors  appear  to  pay  but  little  attention  to  the  rule  where  the 
pressure  is  below  550  volts.  Where  the  pressure  is  in  excess  of  550  volts, 
however,  thorough  grounding  is  generally  insisted  upon.  Inasmuch  as 
the  majority  of  modern  electrical  generators  are  directly  connected  to  their 
prime  movers  and  are  thereby  thoroughly  grounded  through  the  piping 
systems  serving  the  prime  movers,  it  is  not  often  that  a  large  generator 
is  not  well  grounded.  Belted  motors  are  frequently  insulated  owing  to 
being  supported  on  timbers  of  either  a  wooden  floor  or  a  ceiling.  Large 
motors  are  usually  mounted  on  a  concrete  foundation  or  on  the  frame  of 
some  machine,  and  in  such  cases  should  be  thoroughly  grounded.  Fre- 
quently small  motors  are  mounted  on  the  frames  of  machine  tools,  and 
in  some  cases  on  small  concrete  foundations,  and  hence  are  not  thoroughly 
insulated,  nor  can  they  be  said  to  be  thoroughly  grounded.  In  such 
applications  the  inspectors  appear  to  ignore  the  ruling  requiring  effective 
insulation  or  grounding  and  pass  such  machines  by  without  comment. 


Timber 


Hole  for  Machine 
Holding  down  Bolt 


Hole  for 
Foundation  Bolt 


FIGS.    1 


•Countersunk  for 
Motor  Bolt  Nut 

AND  2 MOTOR  INSULATED  ON  A  PARALLEL  TIMBER  BASE  AND  ARRANGE- 
MENT OF  BOLT  HOLES  IN  INSULATING  TIMBERS. 


The  most  common  method  of  insulating  generators  and  motors  is  by 
supporting  them  on  wooden  timbers.  The  wooden-base  frames  used 
for  this  purpose  should  be  thoroughly  filled  and  varnished.  Almost  any 
sort  of  wood  will  do.  Where  a  wooden  floor  or  ceiling  is  depended  on  for 
insulation  it  should  be  thoroughly  filled  and  varnished  to  prevent  the 
entrance  of  moisture,  although  it  is  not  often  that  such  precautions  are 
taken  in  actual  practice.  A  typical  installation  of  a  belted  unit  insu- 
lated on  timbers  is  shown  in  Fig.  1.  The  timbers  are  held  to  the  concrete 
foundation  with  long  foundation  bolts,  and  additional  bolts  secure  the 
machine  frame,  or  the  slide  rails,  to  the  timbers.  It  is  essential  that 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


271 


the  foundation  bolts  and  the  bolts  that  fasten  the  machine  be  well  insu- 
lated from  each  other.  Fig.  2  shows  the  arrangement  of  the  bolt  holes 
in  the  ends  of  timbers  like  those  shown  in  Fig.  1,  indicating  that  a  suffi- 
cient section  of  wood  must  be  provided  between  the  two  holes  to  obtain 
adequate  insulation.  This  section  in  no  case  should  be  less  than  1  in., 
and  a  greater  separation  is  preferable.  As  indicated  in  Fig.  2,  it  is 
necessary  to  countersink  the  holes  for  all  of  the  bolts  so  that  the  bolt  head 
or  the  nut,  as  the  case  may  be,  rests  well  below  the  surface  of  the  timber. 
If  such  holes  are  not  countersunk,  the  metal  of  the  bolt  may  come  in 
contact  with  either  the  foundation  top  or  the  machine  frame  and  defeat 
the  purpose  for  which  the  insulating  timber  is  employed. 

Another  type  of  insulating  base  frame  that  is  frequently  used,  which 
consists  of  four  sticks  held  together  at  their  ends  by  ''half-and-half" 

Slide  Rail 


Holes  for 
Holding  do 
Bo 

"     Pitch 


Countersunk  Bolts 
Holding  Frame  together 


FIGS.    3  AND  4. INSULATING    BASE    FRAME    AND    METHOD    OF    INSULATING    SLIDE 

RAIL. 


joints,  is  shown  in  Fig.  3.  Although  base  frames  of  this  form  are  more 
popular  than  those  like  that  indicated  in  Fig.  1,  they  are  not  as  desirable 
because  dirt  and  oil  are  apt  to  accumulate  in  the  box-like  cavity  formed 
by  the  four  timbers.  It  is  often  very  difficult  to  remove  such  debris. 
With  the  arrangement  of  Fig.  1,  however,  the  dirt  can  be  pushed  out 
from  the  machine  frame  at  either  end,  and  the  floor  or  foundation  under 
the  machine  can  be  kept  clean  with  little  difficulty.  If  dirt  is  allowed  to 
accumulate,  it  may  defeat  the  purpose  for  which  the  timbers  were  placed, 
because  the  timbers  may  become  impregnated  with  it,  which  will  reduce 
their  insulating  qualities. 

The  insulating  frame  that  was  installed  under  a  large  low-voltage 
belted  alternator  is  shown  in  Fig.  5.  For  this  application  an  extremely 
heavy  timber  frame  was  required  because  of  the  size  of  the  machine, 


272 


HANDBOOK  OF  ELECTRICAL  METHODS 


which  was  almost  11  ft.  long.  After  the  10-in.  by  10-in.  sticks  composing 
the  sills  for  the  frame  were  in  place  and  held  down  with  the  foundation 
bolts,  a  double  floor  of  2-in.  by  2-in.  wood  planks  was  nailed  to  the  sills, 
and  on  this  floor  the  generator  was  supported,  the  slide  rails  for  it  being 
held  down  with  lag  screws  turning  through  the  floor  and  down  into  the 
sills. 


Plan  View 
FIG.    5. INSULATING  BASE  FOR  A  LOW-VOLTAGE  GENERATOR. 

There  are  often  cases  where  Underwriters'  inspectors  have  insisted 
that  the  lag  screws  holding  the  slide  rails  of  the  machine  to  the  wooden- 
base  frame  be  thoroughly  insulated  from  the  slide  rails.  The  arrange- 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


273 


ment  that  has  been  used  in  such  cases  is  shown  in  Fig.  4.  The  insulating 
washers  and  bushings  were  turned  from  fiber.  The  wrought-iron  washer 
should  always  be  placed  on  top  of  the  fiber  washer,  as  suggested  in  the 
picture,  to  prevent  the  head  of  the  lag  screw  from  digging  into  the  fiber. 
In  the  installation  illustrated  the  countersunk  holes  in  which  the  nuts  on 
the  ends  of  the  foundation  bolts  turn  were  filled  with  pitch  to  insure 
further  protection. 


Material 


End  Elevation  Section 

FIG.    6. TYPICAL  INSULATING  COUPLING. 

Where  a  motor  or  generator  that  is  directly  connected  to  some  prime 
mover  or  machine  must  be  insulated  therefrom,  it  is  necessary  to  insert 
an  insulating  coupling  in  the  shaft  between  the  electrical  machine  and  the 
other  machine.  The  construction  of  one  type  of  such  a  coupling  is  out- 
lined in  Fig.  6.  A  disk,  usually  of  fiber,  is  bolted  between  the  two  faces 
of  the  flanged  coupling,  and  the  coupling  bolts  are  insulated  with  washers 
and  bushings,  which  are  also  usually  made  of  fiber.  Couplings  of  the 
type  outlined  in  Fig.  6  are  not  self-aligning;  i.e.,  the  only  members  that 


FIG.    7. GROUNDING  A  MACHINE  FRAME  ON  A  PIPE  AND  ON  A  GROUND  PLATE. 

prevent  the  two  shafts  from  being  forced  out  of  line  with  each  other  are 
the  bolts  through  the  coupling.  It  is  necessary,  therefore,  where  a 
coupling  of  this  type  is  used,  to  have  a  bearing  supporting  the  shaft 
reasonably  close  to  and  at  each  side  of  the  coupling.  It  is  difficult  to 
design  an  insulated  self-aligning  coupling,  and  where  one  is  designed  it  is 
ordinarily  quite  expensive.  Hence  it  is  usually  cheaper  to  provide  the 
additional  bearings  required  with  a  coupling  of  simple  construction,  like 


274 


HANDBOOK  OF  ELECTRICAL  METHODS 


that  of  Fig.  6,  than  it  is  to  install  a  self-aligning  bearing  and  thereby 
eliminate  possibly  one  or  two  bearings. 

It  is  practically  impossible  to  insulate  a  large  heavy  direct-connected 
electrical  machine  in  such  a  way  that  it  will  remain  in  accurate  alignment 
with  the  prime  mover  that  drives  it  or  the  machine  that  it  drives.  For 
this  reason  it  is  the  almost  invariable  practice  to  ground  such  machines. 

Where  belt-driven  electrical  machine  frames  are  insulated  from  the 
ground,  trouble  frequently  results  from  static  electricity  generated  by  belt 
friction,  which,  because  it  cannot  find  a  low  resistance  path  to  ground 
through  the  machine  frame,  will  discharge  from  the  belt  driving  or  being 
driven  by  the  machine,  or  may  discharge  from  some  portion  of  the  machine 
frame  to  a  grounded  object.  While  these  static  discharges  may  not  be 
dangerous  to  life,  it  has  been  found  that  they  frequently  have  an  injurious 


FIG.    8. MOTOR  FRAME  GROUNDED  TO  SPRINKLER  PIPE. 

effect  on  the  insulation  used  on  the  windings  and  sometimes  cause  break- 
downs. A  metallic  comb,  connected  to  ground,  arranged  close  to  but  not 
touching  the  belt  that  tends  to  discharge  static  electricity,  will  usually 
eliminate  the  discharges,  or  grounding  the  frame  of  the  machine,  if  ground- 
ing is  permitted,  should  accomplish  the  same  result.  If  direct  grounding 
of  the  frame  is  not  permitted,  a  high  resistance  ground,  consisting  of  a  long 
piece  of  ground-glass  having  a  lead-pencil  mark  on  it,  possibty  an  inch 
can  be  used  in  series  between  the  generator  frame  and  the  ground.  A 
sheet-metal  terminal  should  make  contact  with  each  end  of  the  pencil 
mark,  and  to  these  metal  terminals  are  connected  respectively  the  leads 
to  the  ground  and  to  the  frame  of  the  machine.  Although  the  resistance 
of  such  a  pencil  mark  is  exceedingly  high,  the  static  electricity  will  readily 
flow  through  it. 

Probably  the  best  method  of  grounding  a  frame  is  to  connect  it  to  a 
water  pipe.     As  noted  above,  the  frames  of  generators  directly  connected 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC. 


275 


to  steam  prime  movers  are  thoroughly  grounded  through  the  steam  and 
exhaust  piping  to  the  engine.  Fig.  7  shows  two  methods  of  ground- 
ing the  frame  of  a  machine.  At  the  left  of  the  arrangement  a  ground 
conductor  is  connected,  in  a  manner  to  be  described  hereinafter,  to  the 
frame  of  the  machine  and  to  a  water  pipe.  At  the  right  the  ground  con- 
ductor connects  to  a  metal  plate  embedded  in  charcoal.  The  method  of 
constructing  a  ground  connection  with  a  metal  plate  and  charcoal  is 
described  in  detail  in  the  National  Electrical  Code.  To  be  effective  the 
charcoal  must  always  be  moist,  and  it  is  not  always  that  this  condition 
can  be  assured.  Where  a  ground  connection  for  any  purpose  is  required 
and  a  water  pipe  is  not  available,  it  now  appears  to  be  the  accepted 
practice  to  drive  a  series  of  ground  pipes  into  the  earth  somewhat  after  the 
manner  indicated  in  Fig.  11. 


Foundation  Bolt 


Sectional  Elevation  Sectional  Elevation 

FIGS.  9  AND  10. METHOD  OF  CONNECTING  GROUND  WIRE  TO  MACHINE,  AND  METHOD 

OF  CONNECTING  GROUND  STRAP  TO  MACHINE. 

In  Fig.  8  is  detailed  an  installation  wherein  a  motor  mounted  on  a 
ceiling  in  an  industrial  plant  is  grounded  to  a  sprinkler  pipe.  In  build- 
ings of  non-fireproof  construction  sprinkler  pipes  are  usually  available 
and  constitute  an  excellent  method  of  securing  a  good  ground.  Some 
judgment  should  be  used  in  grounding  a  motor  frame  to  a  sprinkler  pipe. 
A  very  large  motor  should  not  be  grounded  on  a  very  small  pipe.  It  is 
probably  permissible  to  ground  a  10-h.p.  or  15-h.p.  motor  to  a  3/4-in. 
branch  pipe,  but  a  50-h.p.  motor  should  be  grounded  on  one  of  at  least 
2 -in.  nominal  diameter.  The  pipe  selected  should  in  every  case  be  of 
such  size  that  there  would  be  no  possibility  of  its  overheating  when  carry- 
ing the  current  which  the  fuses  protecting  the  motor  will  safely  convey. 


276 


HANDBOOK  OF  ELECTRICAL  METHODS 


Obviously,  if  the  current  through  the  motor  frame  and  ground  wire  to 
the  sprinkler  pipe  comes  greater  than  that  which  the  motor  fuses  will 
pass,  the  fuses  will  blow  and  open  the  circuit. 

A  system  of  ground  pipes  for  grounding  a  large  capacity  electrical 
machine  in  a  location  where  no  water  pipe  is  available  is  outlined  in  Fig. 
11.  A  series  of  ground  pipes,  which  should  extend  far  enough  into  the 
earth  so  that  a  good  portion  of  their  lower  ends  will  always  be  in  damp 
soil  are  driven  into  the  ground  around  the  foundation  of  the  machine 

Wroupht  Iron 
Bolt 


Sectional  Elevation 


f    - 
G  round  ^/"  < 

_^--- 

"x 

f 

Foundation 

"^1               • 

Foundation 
Bolts 

tN 

^Ground 
/  Pipes 

]/ 

4) 

/     \ 

© 
/ 

X 

-.-©.—  - 

Elevation 


Plan  View 

FIG.    11  AND   12.    ARRANGEMENT  OF  GROUND  PIPE  AROUNR  AN  ISOLATED  MACHINE, 
AND  METHOD  OF  CONNECTING  GROUND  STRAP  TO  PIPE. 

These  pipes  are  all  connected  in  multiple  with  a  heavy  ground  wire,  one 
end  of  which  is  carried  up  to  and  connected  on  the  frame  of  the  machine. 
It  should  be  understood  that  this  multiple  ground-pipe  connection  is 
not  nearly  so  good  a  one  as  that  provided  by  a  pipe  connecting  to  an 
extensive  water  system. 

Figs.  9  and  10  show  two  methods  of  connecting  ground  conductors 
to  frames  of  electrical  machines.  In  Fig.  9  a  ground  wire  is  shown. 
Where  wire  is  used  it  should  always  be  of  sufficient  section  to  carry,  with- 
out appreciable  heating,  the  current  that  the  fuses  protecting  the  machine 


MOTORS,  MOTOR  SWITCHES,  GENERATORS,  ETC.  277 

will  pass.  It  should  also  be  of  such  size  that  it  cannot  be  accidentally 
broken.  The  wire  is  clamped  between  two  punched  washers  by  a  nut 
turning  on  the  bolt  that  holds  the  base  of  the  machine  to  the  foundation. 
These  punched  washers  should  be  used  to  insure  effective  clamping,  and 
so  that  the  nut  in  being  turned  on  the  bolt  will  not  dig  into  the  wire.  It 
is  a  good  plan  to  provide,  as  shown,  a  lock  nut  on  top  of  the  first  nut 
which  will  prevent  loosening  if  there  is  vibration.  Sometimes  the  two 
punched  washers  and  the  end  of  the  ground  wire  are  " tinned"  in  order 
to  prevent  the  corrosion  that  might  otherwise  be  caused  at  the  point  of 
contact  between  the  bare  copper  and  iron.  The  end  of  the  ground  wire 
should  be  bent  around  the  bolt  in  the  same  direction  that  the  nuts  turn 
on — that  is,  in  a  right-handed  direction — so  that  any  twisting  action 
due  to  the  nuts  will  tend  to  wrap  the  wire  around  the  bolt  rather  than  to 
unwrap  it.  Copper  should  always  be  used  for  ground  wire. 

A  strap  of  copper  is  used  for  the  ground  connection  of  Fig.  10.  In 
general,  the  requirements  for  the  strap  as  regards  mechanical  strength  and 
current -carrying  capacity  are  the  same  as  those  for  a  ground  wire,  as  out- 
lined in  the  above  paragraph.  Where  a  large  machine  is  being  installed 
a  strap  connection  is  preferable  to  a  wire,  because  with  it  sufficient  cross- 
section  can  be  secured  in  a  form  that  can  be  readily  bent  into  any  de- 
sired contour.  A  large  round  wire  cannot  be  conveniently  formed 
around  the  foundation,  into  the  corners  and  around  the  bends  which  it 
must  follow  in  its  route  to  the  earth.  Where  a  strap  is  used  it  can  be  of 
possibly  1/8-in.  thickness  and  of  sufficient  width  to  provide  the  necessary 
current-carrying  capacity,  and  it  can  always  be  formed  without  difficulty 
into  any  desired  contour.  The  end  of  the  strap  clamped  between  the 
punched  washers  and  the  washers  themselves  should  be  " tinned"  to 
prevent  corrosion. 

A  ground  wire,  if  it  be  not  too  large,  can  be  connected  to  the  ground 
pipe  with  one  of  the  specially  designed  clamps  of  which  there  are  many 
forms  in  the  market.  If  clamps  are  not  available,  the  point  on  the  pipe 
at  which  it  is  desired  to  connect  the  ground  wire  should  be  carefully 
cleaned,  and  the  ground  wire  can  be  soldered  thereto.  In  soldering  a 
copper  wire  to  an  iron  pipe,  the  pipe  should  be  filed  until  it  is  bright  and 
should  be  " tinned"  by  heating  it,  using  powdered  sal  ammoniac  as  a 
flux  and  applying  the  solder.  The  previously  "tinned "  end  of  the  ground 
wire  is  then  wrapped  around  the  pipe  several  times,  the  whole  heated  and 
solder  applied. 

A  ground  strap  can  be  connected  to  a  pipe  as  detailed  in  Fig.  12. 
The  pipe  should  be  clean  at  the  point  where  the  strap  clamps  around  it, 
and  both  the  strap  and  the  pipe  should  preferably  be  "tinned." 


INDEX 


Advertising  lighting  (See  Signs  and  dis- 
play lighting) 

novelty  using  lantern  and   mirror, 
114 

Alarms  (See  Signal  and  alarm  systems) 

Ammeter  testing,  65 

Armatures  (See  Motors  and  generators; 
also  Testing) 

Auto-transformers  (See  Transformers) 


B 


Balancer,  adjusted  for  neutral  regulation 

with  Tirrill  regulator,  86 
set  used  to  bring  up  low  battery  cells, 

102 

Bell  with  automatic  extension,  134 
Bolts,  casting  in  concrete  walls,  89 
Busbars,  method  for  bending,  90 


Cables  (See  Wires  and  cables) 

Ceiling  surfaces  for  indirect  lighting,  111 

Cell  with  relay  auxiliary  contact  for 
checking,  101 

Central  station  construction  and  equip- 
ment, colored  wire  for  switch- 
boards and  panels,  94 

Circuit-breakers,  troubles  due  to  non-use 
of  circuit-breakers,  170 

Coils  (See  Motors  and  generators;  also 
Testing) 

Cold-storage  room  wiring,  198 

Commutators  (See  Motors  and  genera- 
tors; also  Testing) 

Concrete,  casting  bolts  in  concrete  walls, 
89 

Conduit  for  interior  wiring  (See  Interior 
wiring) 

Conduits,  adapting  manhole  to  new  street 

grade,  1 

notes  on  underground  conduit  con- 
struction, 2 


Conduits,     screen    cover    for     manhole 

workers,  1 

Corrosion-proof  wiring,  200 
Cranes,  safety  panel  for  cranes,  258 


D 


Disconnect  switches,  eye  lugs  for,  103 
Display  lighting  (See  Signs  and  display 

lighting) 
Distribution  rack,  104 

systems,  application  of  Tirrill  regu- 
lator to  adjust  balancer  for 
neutral  regulation  at  distant 
point,  86 

arrangement  of  Tirrill  regulator 
to  compensate  for  adjustable 
range  of  terminal  pressure,  87 

circuit  with  shifting  neutral  im- 
proved by  installation  of  auto- 
transformer,  85 

connection  board  for  metering 
power,  95 

connections  for  obtaining  feeder 
voltage  records,  97 

determining  the  power  factor  of 
a  three-phase  circuit,  81 

interchangeable  connections  for 
feeder  resistance,  84 

operation  of  a  two-phase  distri- 
bution system,  77 

paralleling  transformer  bank  on 
star-delta  system,  164 

polyphase  feeder-regulator  motors 
operated  from  single-phase  feed- 
er circuit,  83 

protecting  secondary  networks 
against  defective  transformers, 
161 

remote  control  of  circuits,  98 

stop-watch  record  of  service  inter- 
ruptions, 100 

three-wire  system  rearranged  to 
reduce  voltage  fluctuations,  85 

voltmeter  test  boxes  at  distribu- 
tion points,  88 


19 


279 


280 


INDEX 


E 


Electrolysis,  protecting  gas  pipes  against 

electrolysis,  13 

Excitation  test  with  lamps,  100 
Eye  lugs  for  disconnect  switches,  103 


Feeder  regulator  disconnect  switch,  102 
resistance,    interchangeable  connec- 
tions for,  84 
voltage  records,  97 
Fixtures     for     lighting     (See    Lighting, 

Lamps  and  Interior  wiring) 
Flat-iron  installation,  182 


G 


Generators  and  motors  (See  Motors  and 

generators) 

Glasses  for  line  inspection,  32 
Ground-return,  single-wire  transmission 

line,  50 

Grounding,  Byllesby  Companies  adopt 
uniform  method  of  grounding, 
16 

combination  brace  and  ground-wire 
bayonet,  37 

ground  wire  shields  prevent  induc- 
tion trouble,  16 

of  bathroom  fixtures,  175 

and  insulating  motors  and  genera- 
tors, 269 

lamp  operation  due     to     accidental 
grounds,  126 

locating  grounds  in  armatures,  252 

making  up  a  ground  wire,  15 

methods  of,  transformer  secondaries 
and  secondary  net  works,  20 

secondaries  at  Denver,  17 

some  notes  on  ground  connections, 
23 


House  wiring  (See  Interior  wiring) 

I 

Indications  by  light  (See  Signal  and  alarm 
systems) 


Insulation  (See  Grounding) 

tests  of  transformers,  155 
Insulators,    changing    35,000-volt    insu- 
lators on  live  circuits,  52 
emergency    strain   insulators    made 

from  glass  insulators,  46 
replacing  insulators  with  50,000-volt 

line  "Hot,"  36 

Interior  wiring,  a  method  of  carrying 
wires  around  bridges  in  old 
houses,  177 

an  improvised  pendant  switch,  228 
automatic   extension   of   connection 

bell,  134 

conduit  systems  in  concrete  build- 
ings, 188 

versus  open  work  in  places,  sub- 
ject to  moisture,  corrosive  fumes, 
steam,  etc.,  200 

connecting  cords  in  sockets,  227 
control  of  house  lamps  from  central 

switch,  132 
electric  iron  installation,  182 

vacuum  cleaner  for  fishing  conduit, 

227 

erection  of  metal  molding,  192 
examining  partition  interiors,  174 
explosion-proof  connector  plug,  176 
grounding     of     bathroom     fixtures, 

175 
home-made    chandelier    hook    and 

loops,  184 

in  cold-storage  rooms,  198 
in  metal  molding,  194 
lighting  fixtures  in  a  bank,  131 
mitering  metal  molding,  191 
one-piece     versus     two-piece     push 

switches,  180 

removing   nails   from   trim   in   old- 
house  wiring,  174 

right  and  wrong  methods  of  connect- 
ing plug  cut-outs,  177 
right  way  to  place  protecting  tubes, 

177 

safety  panel  for  cranes,  258 
simplifying  concealed  conduit  work, 

186 
support  of  cables  for  interior  work, 

175 

use  of  single-pole  switches,  179 
wiring   buildings   with    cinder-filled 
floors,  183 


INDEX 


281 


Interior  wiring,  for  extension  lamp  in 
600-volt  series  circuit,  151 

Interruptions  (See  Stop-watch  record  of 
service) 


Lamp-cord  adjusters,  118 

operation  due  to  accidental  grounds, 
126 

signal  system  for  a  hospital,  130 
for  a  restaurant,  129 

signals  for  hotel  maids,  129 
Lamps,  all-day  supervision  of  arc  circuits, 
136 

connecting  cords  in  sockets,  227 

control  of  house  lamps  from  central 
switch,  132 

cradle  clamp  for  hanging  arc  lamps, 
119 

danger  of  broken  lamp  near  inflam- 
mable material,  113 

economical  street-lighting  wiring 
arrangement,  134 

for  synchronizing  bank,  100 

for  places  subject  to  moisture,  corro- 
sive fumes,  steam,  etc.,  200 

holder  for  removing  street  series 
receptacles,  118 

inexpensive  lamp  guard  for  inter- 
urban  cars,  151 

kink  to  save  lamps  on  series-multiple 
circuits,  110 

lighting  fixtures  in  a  bank,  131 

lighting  one  lamp  on  four-lamp  fix- 
tures with  three-wire  system, 
116 

locating  faults  on  series  lighting 
circuits,  127 

mercury-vapor-incandescent  lamp 
cabinet  for  photographic  work, 
132 

operation  of  series  alternating-cur- 
rent street  arc  lamps,  120 

overcoming  over-load  on  series  arc- 
lamp  circuits,  125 

protection  with  netting,  117 

raising  heights  of  lamp-posts,  53 

rubber  band  to  prevent  backing  out, 
117 

testing,  with  a  motor-driven  machine, 
150 


Lamps,  types  and  uses  of  semi-indirect 
lighting  units,  152 

wiring    for    extension,    in    600-volt 

series  circuit,  151 

Lighting,     all-day     supervision     of     arc 
circuits,  136 

automatic  control  of  curb  lighting 
fed  from  Edison  system,  136 

ceiling  surfaces  on  indirect  system, 
111 

control  of  house  lamps  from  central 
switch,  132 

economical  street-, wiring  arrange- 
ment, 134 

electric,  from  three-phase  circuits, 
139 

fixtures  for  places  subject  to  mois- 
ture,   corrosive    fumes,    steam, 
etc.,  200 
in  a  bank,  131 

holder  for  removing  street  series 
receptacles,  118 

locating  faults  on  series  lighting 
circuits,  127 

one  lamp  on  four-lamp  fixtures  with 
three- wire  system,  116 

operation  of  series  alternating-cur- 
rent street  arc  lamps,  120 
of  tub-transformer  secondaries  in 
series,  163 

overcoming  overload  on  series  arc- 
lamp  circuits,  125 

remote-controlled  operation  of 
Peoria's  ornamental  lighting, 
138 

two-phase  wiring  cured  low-fre- 
quency flicker,  150 

types  and  uses  of  semi-indirect 
lighting  units,  152 

wiring  for  extension  lamp  in  600-volt 

series  circuit,  151 
Lightning    arresters,    concrete    resistors 

for,  52 
maintenance  of  electrolytic,  45 

protection,  adaptation  of  three-phase 

arrester  for  two-phase  use,  44 
use   of  choke  coils  with  pole  ar- 
resters, 44 

Line  construction,  battery  search  lantern 
for  linemen,  33 

combination  brace  and  ground  wire 
bayonet,  37 


282 


INDEX 


Line  construction,  corner,  for  50,000-volt 
line,  37 

high-tension  crossing  with  protec- 
tive loop,  42 

inspecting  inaccessible  places  with 
optical  aids,  32 

operating  results  with  a  2300-volt 
single- wire,  ground-ret  urn  trans- 
mission line,  50 

raising  the  height  of  old  inclosed- 
arc  lamp-posts  at  Cincinnati, 
Ohio,  53 

simple  method  of  transposing  wires, 
43 

support  of  long  transmission  span 
by  messenger  cable,  55 

trouble  man's  portable  search-lamp, 
33 

use  of  choke  coils  with  pole  arres- 
ters, 44 
Lugs  for  disconnect  switches,  103 


M 


Manhole,    adapting    manholes    to    new 
street  grade,  1 

screen  cover  for  manhole,  1 
Meter,  a  labor-saving  meter  truck,  56 

a  portable  stand  for  graphic  instru- 
ments, 72 

ammeter  testing,  65 

compartments     for     meters     under 
test,  74 

connection     board      for      metering 
power,  95 

ohmic  and  inductive  resistances  of 
meter-current  circuits,  60 

pendulum  'counting  device  for  test- 
ing meters,  62 

protection  of  electric  meters,  56 

tagging  meter  loops,  56 

testing  shunt-type  watt-hour  meters, 
64 

two-meter    off-peak    rate    at     Salt 
Lake  City,  58 

use   of    single-phase    wattmeter    on 
polyphase  circuit,  58 

voltmeter  test  boxes  at  distribution 
points,  88 

watt-hour  meter  testing  for  cential 

stations,  74 
Moisture-proof  wiring,  198-200 


Molding  (See  Interior  wiring) 
Motors  and  generators,  adjusting  inter- 
pole  fields  of  generator,  245 
care  of  electric  motors,  239 
commutator  testing  device,  249 
conversion  of  550-volt  generator  to 

Edison  three-wire  service,  253 
electric    welding    of    broken    motor 

shaft,  237 
installation     of     motors     in     dirty 

places,  229 
installing  motors  under  severe  dust 

conditions,  230 
insulating  and  grounding,  269 
locating  grounds  in  armatures,  252 
method  of  raising  inverted  motors, 

255 

motors    housed    in    external    sheet- 
iron,  229 
mounting  motors  on  side-walls  and 

columns,  260 

rebabbitting  motor  bearings,  238 
remedying  trouble  caused  by  vary- 
ing voltage,  253 

repairing  a  broken  motor  leg,  236 
starting  torque  of  induction  motors, 

242 
supporting     motors     on     concrete 

building  ceilings,  232 
testing  armatures  with  alternating 

current,  251 

magnet  coils  for  short-circuits,  248 
polarity  of  field  coils,  248 
troubles  with  induction  motors,  240 
turning  down  a  commutator,  244 
wiring  equipment  for  motor  testing, 

246 

100-volt  shunt  motor  on  a  220-volt 
three-wire  circuit,  254 


Open  wiring  (See  Conduit,  versus  open 
wiring  for  places  subject  to 
moisture,  corrosive  fumes, 
steam,  etc.,  200 


Photographic  work  with  modified  mer- 
cury-vapor-incandescent lamp, 
132 


INDEX 


283 


Poles,  blasting  holes  for,  with  dynamite,  33 
bucket  for  bailing  pole  holes,  33 
concrete  poles  integral  with  building 

to  save  space,  48 
cross-arms  made  of  old  pipe,  35 
numbering  system  for  pins  and  cross- 
arms,  34 

pole-height  estimator,  32 
temporary  cross-arm  braces  to  aid 

construction  crews,  48 
Polyphase  feeder-regulator  motors  oper- 
ated   from    single-phase    feeder 
circuit,  83 
Portable  stand  for  graphic  instruments, 

72 

Power   factor,    determination   on   three- 
phase  circuit,  81 


R 


Rack,  iron-pipe  for  distribution,  104 
Relay   auxiliary   contact   for   aluminum 

check  cell,  101- 
Remote  control  of  circuits,  98 

switches  for  flat-rate  signs,  105 
Rheostats,  handy,  portable,  14 


S 


Safety  devices,  lamp  guard  for  interurban 

cars,  151 

protecting        secondary        network 
against  defective  transformers, 
161 
protection  of  lamps  with  wire  netting 

117 

screen  cover  for  manhole  workers,  1 
Salt-air  proof  wiring,  200 
Service  interruptions,  stop-watch  record 

of,  100 

Showcases,  electrically  lighted,  110 
Signs  and  display  lighting,  a  kink  to  save 
lamps,   series-multiple   circuits, 
110 

electric-lighted    showcase    for    the 

plate-glass  storeroom  door,  110 

flat-rate         with         remote-control 

switches,  105 
illuminated  church  sign,  108 

sign  using  flaming-arc  lamps,  109 
interchangeable  illuminated  sidewalk 
sign,  106 


Signs,  lighting  a  Chicago  store  window, 

111 
projecting-lantern  advertising  sheet, 

114 

remote-controlled       operation       of 
Peoria's  ornamental  lighting,  138 
running  boards  for  a  Tungsten  light- 
ing installation,  107 
throwing  light  on  object  to  be  sold, 

115 

Signal   and   alarm   systems,    alarm   con- 
nection for  transformers,  171 
alarm  to  indicate  operation  of  remote 

rectifier  set,  97 
automatic  extension  of  connecting 

bell,  134 

lamp  signals  for  hotel  maids,  129 
signal  system  for  a  hospital,  130 

for  a  restaurant,  129 
Soldering,  methods  of  soldering  wires  in 

terminal  lugs,  9 
soldered  wire  connections,  11 
with  blow  torch  and  iron,  12 
Spark-gaps  (bridged)  protect  transformer 

coils,  160 

Splicing  wires  and  cables,  38 
Station  construction  and  equipment,   a 
method  for  bending  busbars,  90 
a  switchboard  wiring  pit,  91 
casting  bolts  in  concrete  walls,  89 
lamps  for  field  excitation  test,  100 
supporting  cables  in  vertical  runs,  89 
synchronizing  bank,  100 
Steam-proof  wiring,  200 
Stop-watch  record  of  service  interrup- 
tions, 100 
Storage  batteries,  balancer  set  used  to 

bring  up  low  battery  cells,  102 
Store  window  lighting,  111 
Switchboards,  alarm  circuit  for  double- 
throw  oil  switches,  98 
to  indicate   operation   of  remote 

rectifier  set,  97 
colored  wire  for,  94 
connection  board  for  metering  power, 

95 
connections    for     obtaining    feeder 

voltage  records,  97 
for  crane,  258 

remote  control  of  circuits,  98 
synchronizing  bank,  100 
wiring  pit,  91 


284 


INDEX 


Switches,  alarm  circuit  for  double-throw 

oil  switches,  98 

an  improvised  pendant  switch,  228 
a  home-made  iron  switch  box,  230 
design  of  wooden  switch-boxes,  231 
disconnect  coupling  for  oil-switch 

leads,  168 

switch  for  feeder  regulators,  102 
low  freezing  mixtures  for  oil,  167 
one-piece     versus     two-piece   push, 

180 
remote   control,   for  flat-rate  signs, 

105 
snap  and  knife,,  for  places   subject 

to   moisture,    corrosive    fumes, 

steam,  etc.,  200 

switch  pull-rods  in  tension  not  com- 
pression, 169 
temporary    repair     to     oil     switch, 

170 
use  of  single-pole  ,  179 


Testing,  armatures  with  alternating  cur- 
rent, 251 
ammeter,  65 

circular  synchronizing  bank,  100 
commutator  testing  device,  249 
current-ratio   and   phase-angle   test 

of  series  transformers,  157 
field  excitation  test  lamps,  100 
lamps  with  a  motor-driven  machine, 

150 

large  watt-hour  meters  on  fluctuat- 
ing loads,  68 
locating    faults    on    series    lighting 

circuits,  127 

magnet  coils  for  short-circuits,  248 
method     of     locating     grounds     in 

armatures,  252 
ohmic   and  inductive    resistence  of 

meter-current  circuits,  60 
pendulum  counting  device  for  testing 

meters,  62 

polarity  of  field  coils,  248 
shunt-type  watt-hour  meters,  64 
starting  torque  of  induction  motors, 

242 
testboard  proof  against   crosses  or 

shorts,  12 
transformers  for  insulation,  155 


Testing,  watt-hour  meter  testing  for  cen- 
tral stations,  74 

wiring  equipment  for  motor  test,  246 
Thawing  a  frozen  pipe  by  electricity,  9 

waterpipes    with    electricity,    6 

waterpipes  without  a  transformer,  7 
Three-phase  lighting  circuits,  139 

-wire  system,  lighting  of  one  lamp 
on  four-lamp  fixtures,  116 

-wire  machine  from  550-volt  gene- 
rator, 253 

system  rearranged  to  reduce  volt- 
age fluctuations,  85 
220-volt  circuit  used  by  110-volt 

shunt  motor,  254 

Tirrill  regulator  used  to  adjust  balancer 
for  neutral  regulation  at  distant 
point,  86 

used  to  compensate  over  adjustable 

range  ot  terminal  pressures,  87 
Transformers,  alarm  connection  for  trans- 
formers, 171 

auto- transformer  used  to  improve 
circuit  with  shifting  neutral, 
85 

auto-transformers  used  for  lighting 
from  three-phase  circuits,  139 

bridged  spark  gaps  protect  trans- 
former coils,  160 

current-ratio  and  phase-angle  test  of 
series  transformers,  157 

inserting  spare  transformer  in  star- 
delta  group,  162 

operation  of  tub-transformer  secon- 
daries in  series,  163 

paralleling  transformer  bank  on 
star-delta  systems,  164 

protecting  secondary  networks 
against  defective  transformers, 
161 

testing  transformers  for  insulation, 
155 

three-transformer  method  of  chang- 
ing from  two  to  three  phases, 
166 

two-phase  to  three-phase  auto-.  172 
Transmission,  (See  Distribution  systems, 
Lightning  protection,  Line  con- 
struction, Insulators,  Poles,  etc. 
Trough  wiring,  200 

Two-phase  wiring  cures  low- frequency 
flicker,  150 


INDEX 


285 


Vacuum  cleaner  used  for  fishing  conduit, 

227 
Voltage    fluctuation    trouble    in    motor 

remedied,  253 
Voltmeter    test    boxes    at    distribution 

points,  88 

W 

Wattmeters,  testing  large  watt-hour 
meters  on  fluctuating  loads,  68 

testing  shunt-type  watt-hour  meters, 
64 

use  of  single-phase  on  polyphase 
circuit,  58 


Wattmeter,  watt-hour  meter  testing  for 

central  stations,  74 
Windows  of  stores   lighted   electrically, 

111 
Wires  and  cables,  a  switchboard  wiring 

pit,  91 
colored  wires  for  switchboards  and 

panels,  94 
methods  of  splicing  wires  and  cables, 

38 
support  of  cables  for  interior  work, 

175 

supporting  cables  in  vertical  runs,  89 
wires  for  places  subject  to  moisture, 

corrosive  fumes,  steam,  etc.,  200 


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